Methods of using transporter-like molecules to treat pain and pain-related disorders

Abstract

The invention relates to OCT-3 polypeptides, nucleic acid molecules encoding OCT-3, and uses thereof. OCT-3 is a protein that is expressed in the plasma membrane of biological cells, across which it regulates the transport of organic molecules.

Description

RELATED APPLICATIONS

[0001] The present application is a divisional application of U.S. patent application Ser. No. 10/000,273, filed Nov. 2, 2001, which is a continuation-in-part of U.S. patent application Ser. No. 09/496,692, filed on Feb. 20, 2000, now U.S. Pat. No. 6,313,271, which is a divisional application of U.S. patent application Ser. No. 08/964,127, filed on Nov. 6, 1997, now U.S. Pat. No. 6,277,565.

BACKGROUND OF THE INVENTION

[0002] In the course of performing their normal physiological functions, many types of cells, including bacterial cells and those in specialized mammalian tissues such as the liver and kidney, transport a variety of organic molecules across their cell membranes. For example, cells in the proximal tubule of the kidney transport glucose, amino acids, and uric acid across their membranes, and work to eliminate various drugs and toxic substances from the body. All of these molecules are transported across the cell membranes by specialized cellular transporters.

[0003] Recently, genes encoding several putative transporters have been identified. These molecules include OCT-1 (organic cation transporter; Grundemann et al., Nature 372:549-552, 1994), OCT-2 (Okuda et al., Biochem. Biophys. Res. Comm. 224:500-507, 1996), NLT (novel liver-specific transporter; Simonson et al., J. Cell Sci. 107:1067-1072, 1994), and NKT (novel kidney-specific transporter; Lopez-Nieto et al., J. Biol. Chem. 272:6471-6478, 1997). While the sequences of these transporters are not highly conserved (at the amino acid level, OCT-1 and NLT are only 30% and 35% identical to NKT, respectively), they do exhibit similar transmembrane (TM) domain hydropathy profiles.

SUMMARY OF THE INVENTION

[0004] The invention described herein relates to the discovery and characterization of oct-3, a gene encoding a protein that transports molecules across the plasma membranes of biological cells. OCT-3 is highly expressed in the neuronal cells of the brain, including, e.g., cells in the cortex and in the hypothalamus. Accordingly, altering the expression or activity of OCT-3 (e.g., with small molecules, antisense molecules, or neutralizing antibodies) can alter the concentration of molecules (such as neurotransmitters) that are present within the cell or in the extracellular spaces around the cell (i.e., on either side of the plasma membrane). Altering the concentrations of these molecules in patients afflicted with certain conditions, including neurodegenerative diseases, behavioral disorders, eating or sleep disorders, and pain responses (e.g., elicited during various forms of tissue injury or in association with musculoskeletal disorders), can provide relief from the symptoms associated with these conditions.

[0005] More specifically, the invention features an isolated nucleic acid molecule (i.e., a nucleic acid molecule that is separated from the 5′ and 3′ coding sequences with which it is immediately contiguous in the naturally occurring genome of an organism) that encodes an OCT-3 polypeptide. As used herein, an OCT-3 polypeptide is a polypeptide that: (1) is expressed in the plasma membrane of a biological cell (e.g., a cell in the kidney, liver, or brain), (2) contains transmembrane (TM) domains, and (3) when functioning normally, transports organic molecules across the plasma membrane. Preferably, the OCT-3 polypeptide has at least 6 transmembrane domains (e.g., 6, 8, or 10 TM domains), and more preferably, has at least 12 TM domains. The OCT-3 polypeptide can be a mammalian polypeptide, i.e., a polypeptide normally expressed by the cells of a mammal, such as a human. In the event the OCT-3 polypeptide is human, it can have the sequence shown in 2 or SEQ ID NO:4, or it can be encoded by nucleic acid molecules having the sequence shown in SEQ ID NO: 1 or SEQ ID NO:3. However, the invention is not limited to nucleic acid molecules and polypeptides that are identical to those SEQ ID NOs. For example, the invention includes nucleic acid molecules which encode splice variants, allelic variants or mutant forms of OCT-3 as well as the proteins encoded by such nucleic acid molecules. Also within the invention are nucleic acid molecules that hybridize under stringent conditions to a nucleic acid molecule having the sequence of SEQ ID NOs: 1, 3, or 5. As described further below, molecules that are substantially identical to SEQ ID NOs: 1-6 are also encompassed.

[0006] The term “substantially pure” as used herein in reference to a given compound (e.g., an OCT-3 polypeptide) means that the compound is substantially free from other compounds, such as those in cellular material, viral material, or culture medium, with which the compound may have been associated (e.g., in the course of production by recombinant DNA techniques or before purification from a natural biological source). When chemically synthesized, a compound of the invention is substantially pure when it is substantially free from the chemical compounds used in the process of its synthesis. Polypeptides or other compounds of interest are substantially free from other compounds when they are within preparations that are at least 60% by weight (dry weight) the compound of interest. Preferably, the preparation is at least 75%, more preferably at least 90%, and most preferably at least 99%, by weight the compound of interest. Purity can be measured by any appropriate standard method, for example, by column chromatography, polyacrylamide gel electrophoresis, or HPLC analysis.

[0007] Where a particular polypeptide or nucleic acid molecule is said to have a specific percent identity to a reference polypeptide or nucleic acid molecule of a defined length, the percent identity is relative to the reference polypeptide or nucleic acid molecule. Thus, a peptide that is 50% identical to a reference polypeptide that is 100 amino acids long can be a 50 amino acid polypeptide that is completely identical to a 50 amino acid long portion of the reference polypeptide. It might also be a 100 amino acid long polypeptide which is 50% identical to the reference polypeptide over its entire length. Of course, many other polypeptides will meet the same criteria. The same rule applies for nucleic acid molecules.

[0008] For polypeptides, the length of the reference polypeptide sequence will generally be at least 16 amino acids, preferably at least 20 amino acids, more preferably at least 25 amino acids, and most preferably 35 amino acids, 50 amino acids, or 100 amino acids. For nucleic acids, the length of the reference nucleic acid sequence will generally be at least 50 nucleotides, preferably at least 60 nucleotides, more preferably at least 75 nucleotides, and most preferably at least 100 nucleotides (e.g., 150, 200, 250, or 300 nucleotides).

[0009] In the case of polypeptide sequences that are less than 100% identical to a reference sequence, the non-identical positions are preferably, but not necessarily, conservative substitutions for the reference sequence. Conservative substitutions typically include substitutions within the following groups: glycine and alanine; valine, isoleucine, and leucine; aspartic acid and glutamic acid; asparagine and glutamine; serine and threonine; lysine and arginine; and phenylalanine and tyrosine.

[0010] Sequence identity can be measured using sequence analysis software (e.g., the Sequence Analysis Software Package of the Genetics Computer Group, University of Wisconsin Biotechnology Center, 1710 University Avenue, Madison, Wis. 53705), with the default parameters as specified therein.

[0011] The invention also features a host cell that includes an isolated nucleic acid molecule encoding OCT-3 (either alone or in conjunction with a heterologous polypeptide, such as a detectable marker), or a nucleic acid vector that contains a sequence encoding OCT-3 (again, with or without a heterologous polypeptide). The vector can be an expression vector, and can include a regulatory element.

[0012] An antibody that specifically binds an OCT-3 polypeptide is also within the scope of the present invention and is useful, for example, to detect OCT-3 in a biological sample, or to alter the activity of OCT-3. For example, OCT-3 can be detected in a biological sample by contacting the sample with an antibody that specifically binds OCT-3 under conditions that allow the formation of an OCT-3-antibody complex and detecting the complex, if present, as an indication of the presence of OCT-3 in the sample. The use of an antibody in a treatment regime, where it can alter the activity of OCT-3, is discussed further below.

[0013] An antibody of the invention can be a monoclonal, polyclonal, or engineered antibody that specifically binds OCT-3 (as described more fully below). An antibody that “specifically binds” to a particular antigen, for example, an OCT-3 polypeptide of the invention, will not substantially recognize or bind to other molecules in a sample, such as a biological sample, that includes OCT-3.

[0014] Given that an object of the present invention is to alter the expression or activity of OCT-3 in vivo, a pharmaceutical composition containing, for example, an isolated nucleic acid molecule encoding OCT-3 (or a fragment thereof), a nucleic acid molecule that is antisense to OCT-3 (i.e., that has a sequence that is the reverse and complement of a portion of the coding strand of an OCT-3 gene), an OCT-3 polypeptide, or an antibody, small molecule, or other compound that specifically binds an OCT-3 polypeptide is also a feature of the invention.

[0015] The discovery and characterization of oct-3 and the polypeptide it encodes makes it possible to determine whether a given disorder is associated with aberrent expression of oct-3 (meaning expression at the level of gene transcription or mRNA translation) or activity of OCT-3. For example, one can diagnose a patient as having a disorder associated with aberrant expression of oct-3 by measuring oct-3 expression in a biological sample obtained from the patient. An increase or decrease in oct-3 expression in the biological sample, compared with oct-3 expression in a control sample (e.g., a sample of the same tissue collected from one or more healthy individuals) indicates that the patient has a disorder associated with aberrant expression of oct-3. Similarly, one can diagnose a patient as having a disorder associated with aberrant activity of OCT-3 by measuring OCT-3 activity in a biological sample obtained from the patient. An increase or decrease in OCT-3 activity in the biological sample as compared with OCT-3 activity in a control sample, indicates that the patient has a disorder associated with aberrant activity of OCT-3. The techniques required to measure gene expression or polypeptide activity are well known to those of ordinary skill in the art.

[0016] In addition to diagnostic methods, such as those described above, the present invention encompasses methods and compositions for typing and evaluating the prognosis, appropriate treatment, and treatment effectiveness of disorders associated with inappropriate expression of oct-3 or inappropriate activity of OCT-3. For example, the nucleic acid molecules of the invention can be used as probes to classify cells in terms of their level of oct-3 expression, or as primers for diagnostic PCR analysis in which mutations, allelic variations, and regulatory defects in the oct-3 gene can be detected. Similarly, those of ordinary skill in the art can use routine techniques to identify inappropriate activity of OCT-3, which can be observed in a variety of forms. For example, inappropriate activity can take the form of an alteration in the rate with which an OCT-3 transporter moves molecules across the plasma membrane, or a difference in the type of molecule that is transported. Diagnostic kits for the practice of such methods are also provided.

[0017] The invention further encompasses transgenic animals that express an oct-3 gene and recombinant “knock-out” animals that fail to express an oct-3 gene. These animals can serve as new and useful models of disorders in which oct-3 is misexpressed.

[0018] The invention also features antagonists and agonists of OCT-3 that can inhibit or stimulate, respectively, one or more of the biological activities of OCT-3. Suitable antagonists can include small molecules (i.e., organic or inorganic compounds with a molecular weight less than about 10,000 grams per mole), large molecules (i.e., molecules with a molecular weight greater than about 10,000 grams per mole), antibodies that specifically bind and “neutralize” OCT-3 (as described below), and nucleic acid molecules that interfere with transcription or translation of OCT-3 (e.g., antisense nucleic acid molecules and ribozymes). Agonists of OCT-3 also include small and large molecules, and antibodies other than neutralizing antibodies.

[0019] The invention also features molecules that can increase or decrease the expression of oct-3 (e.g., by altering transcription or translation). Small molecules (as defined above), large molecules (as defined above), and nucleic acid molecules (e.g., antisense and ribozyme molecules) can be used to inhibit the expression of an oct-3 gene. Other types of nucleic acid molecules (e.g., molecules that bind to oct-3 transcriptional regulatory sequences) can be used to increase the expression of an oct-3 gene.

[0020] Compounds that modulate the expression of oct-3 in a cell can be identified by comparing the level of expression of oct-3 in the presence of a selected compound with the level of expression of oct-3 in the absence of that compound. A difference in the level of oct-3 expression indicates that the selected compound modulates the expression of oct-3 in the cell. A comparable test for compounds that modulate the activity of OCT-3 can be carried out by comparing the level of OCT-3 activity in the presence and absence of the compound.

[0021] Patients who have a neurological disorder mediated by abnormal OCT-3 activity can be treated by administration of a compound that alters the expression of the oct-3 gene or the activity of the OCT-3 protein. When the objective is to decrease expression or activity, the compound administered can be an oct-3 antisense oligonucleotide, an antibody, such as a neutralizing antibody, or an antagonist that specifically binds oct-3 or OCT-3, respectively.

[0022] A wide variety of OCT-3 mediated neurological disorders are amenable to treatment according to the methods set forth herein. For example, the neurological disorder can be a neurodegenerative disease, such as Parkinson's Disease, Huntington's Disease, or Alzheimer's Disease. Alternatively, the neurological disorder can be characterized by abnormal behavior or mood disorders. For example, the patient may suffer from depression, anxiety, or schizophrenia. A patient who has a sleep disorder or a weight disorder, such as a patient who is obese or who is suffering from a wasting disorder (as often occurs in the event of AIDS) can also be treated by administration of a compound that alters the expression of oct-3 or the activity of OCT-3. The neurological disorder can be pain, e.g., pain response elicited during various forms of tissue injury, e.g., inflammation, infection, and ischemia, usually referred to as hyperalgesia (described in, for example, Fields, H. L. (1987) Pain, New York:McGraw-Hill), pain associated with musculoskeletal disorders, e.g., joint pain; tooth pain; headaches; and pain associated with surgery, rheumatoid arthritis, viral infection, allergic reaction, asthma, chronic pain, chronic pancreatitis, somatoform disorders, fibromyalgia syndrome; and neuropathic pain, allodynia, and hyperesthesia. A detailed description of these methods of treatment is set forth below.

[0023] The preferred methods and materials are described below in examples which are meant to illustrate, not limit, the invention. Skilled artisans will recognize methods and materials that are similar or equivalent to those described herein, and that can be used in the practice or testing of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described herein. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In addition, the materials, methods, and examples are illustrative only and are not intended to be limiting.

[0025] Other features and advantages of the invention will be apparent from the detailed description and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIGS. 1A-1C are a depiction of a human oct-3 nucleotide sequence (including 3′ and 5′ non-translated sequence; SEQ ID NO: 1) that encodes an OCT-3 polypeptide with 12 transmembrane domains (SEQ ID NO:2).

[0027] FIGS. 2A-2B are a depiction of a human oct-3 nucleotide sequence (including 3′ and 5′ non-translated sequence; SEQ ID NO:3) that encodes an OCT-3 polypeptide with 6 TM domains (SEQ ID NO:4).

[0028] FIGS. 3A-3B are a depiction of a rat oct-3 nucleotide sequence (SEQ ID NO:5) encoding a rat OCT-3 polypeptide (SEQ ID NO:6). This polypeptide does not appear to be full-length.

[0029] FIGS. 4A-4E are representations of regions of amino acids in the OCT-3 polypeptide (SEQ ID NO:2) that conform to consensus sequences derived from polypeptides in the OCT family. Alternative residues for each consensus sequence are shown on the uppermost line. The OCT-3 sequence shown in FIG. 4A is found in the second transmembrane domain and continues between the second and third TM domains (at about residues 119 to 128 of SEQ ID NO:2, also shown in SEQ ID NO:8) and is aligned against the OCT consensus sequence shown in SEQ ID NO:7; the OCT-3 sequence shown in FIG. 4B is found in the in the fourth transmembrane domain and continues between the fourth and fifth TM domains (at about residues 158 to 185 of SEQ ID NO:2, also shown in SEQ ID NO: 11) and is aligned against the OCT consensus sequence shown in SEQ ID NO: 10; the OCT-3 sequence shown in FIG. 4C is found between the sixth and seventh TM domains (at about residues 237 to 243 of SEQ ID NO:2, also shown in SEQ ID NO: 13) and is aligned against the OCT consensus sequence shown in SEQ ID NO:12; the OCT-3 sequence shown in FIG. 4D is found C-terminal to the twelfth TM domain (at about residues 474 to 479 of SEQ ID NO:2) and is aligned against the OCT consensus sequence shown in SEQ ID NO: 14; and the OCT-3 sequence shown in FIG. 4E is found in the tenth transmembrane domain and continues between the tenth and eleventh TM domains (at about residues 415 to 428 of SEQ ID NO:2, also shown in SEQ ID NO: 17) and is aligned against the OCT consensus sequence shown in SEQ ID NO: 16.

DETAILED DESCRIPTION

[0030] As described above, the nucleic acid molecules of the invention and the polypeptides they encode (e.g., OCT-3 polypeptides and fragments thereof) can be used directly as diagnostic and therapeutic agents, or they can be used to generate antibodies or identify small or large molecules that, in turn, are clinically useful. In addition, oct-3 nucleic acid molecules are useful in genetic mapping of the chromosomal location of oct-3, and as tissue-specific (e.g., neuronal-specific) markers. Accordingly, expression vectors containing the nucleic acid molecules of the invention, cells transfected with these vectors, the polypeptides expressed, and antibodies generated, against either the entire polypeptide or an antigenic fragment thereof, are among the preferred embodiments. These embodiments and their clinical application are described further below.

[0031] Nucleic Acid Molecules Encoding OCT-3

[0032] The oct-3 nucleic acid molecules of the invention can be cDNA, genomic DNA, synthetic DNA, or RNA, and can be double-stranded or single-stranded. In the event the nucleic acid molecule is single-stranded, it can be either a sense or an antisense strand. Fragments of these molecules are also considered within the scope of the invention, and can be produced, for example, by polymerase chain reaction (PCR), or generated by treating a longer fragment (e.g., a full-length oct-3 gene sequence) with one or more restriction endonucleases. Similarly, a full-length oct-3 RNA molecule, or a fragment thereof, can be produced by in vitro transcription. The isolated nucleic acid molecule of the invention can encode a fragment of OCT-3 that is not found as such in the natural state. Although nucleic acid molecules encoding any given fragment of OCT-3 are within the scope of the invention, fragments that retain the biological activity of OCT-3 (as assessed below) are preferred.

[0033] The nucleic acid molecules of the invention encompass recombinant molecules, such as those in which a nucleic acid molecule (e.g., an isolated nucleic acid molecule encoding OCT-3, or a fragment thereof) is incorporated: (1) into a vector (e.g., a plasmid or viral vector), (2) into the genome of a heterologous cell, or (3) into the genome of a homologous cell, at a position other than the natural chromosomal location. Recombinant nucleic acid molecules, transgenic animals, and uses therefor are discussed further below.

[0034] The nucleic acid molecules of the invention can contain naturally occurring sequences, or sequences that differ from those that occur naturally, but, due to the degeneracy of the genetic code, encode the same polypeptide (e.g., the polypeptides of SEQ ID NOs:2, 4, or 6). In addition, the nucleic acid molecules of the invention are not limited to those that encode the amino acid residues of the OCT-3 polypeptide as shown is SEQ ID NOs:2, 4, or 6, they can also include some or all of the non-coding sequences that lie upstream or downstream from an oct-3 coding sequence, a heterologous regulatory element, or a sequence encoding a heterologous polypeptide (e.g., a reporter gene). Regulatory elements and reporter genes are discussed further below.

[0035] The nucleic acid molecules of the invention can be synthesized (for example, by phosphoramidite-based synthesis) or obtained from a biological cell, such as the cell of a mammal. Thus, the nucleic acids can be those of a human, mouse, rat, guinea pig, cow, sheep, goat, horse, pig, rabbit, monkey, dog, or cat. Combinations or modifications of the nucleotides within these types of nucleic acid molecules are also encompassed.

[0036] In the event the nucleic acid molecules of the invention encode or act as antisense molecules, they can be used, for example, to regulate translation of oct-3 mRNA. Techniques associated with detection of nucleic acid sequences or regulation of their expression are well known to persons of ordinary skill in the art, and can be used in the context of the present invention to diagnose or treat disorders associated with aberrant oct-3 expression. However, aberrent expression of oct-3 (or aberrent activity of OCT-3) is not a prerequisite for treatment according to the methods of the invention; the molecules of the invention (including the nucleic acid molecules described here) are expected to be useful in improving the symptoms associated with a variety of medical conditions (particularly neurological disorders) regardless of whether or not the expression of oct-3 (or the activity of OCT-3) is detectably aberrent. Nucleic acid molecules are discussed further below in the context of their clinical utility.

[0037] The invention also encompasses nucleic acid molecules that encode other members of the OCT-3 family. Such nucleic acid molecules will be readily identified by the ability to hybridize under stringent conditions to a nucleic acid molecule encoding an OCT-3 polypeptide (e.g., the sequence shown in SEQ ID NOs: 1, 3, or 5). The cDNA sequences described herein (SEQ ID NOs: 1, 3, and 5) can be used to identify these nucleic acids, which include, for example, nucleic acids that encode homologous polypeptides in other species, splice variants of the oct-3 gene in humans or other mammals, allelic variants of the oct-3 gene in humans or other mammals, and mutant forms of the oct-3 gene in humans or other mammals.

[0038] The preferred class of nucleic acid molecules that hybridize to SEQ ID NOs: 1 and 3 are nucleic acid molecules that encode human allelic variants of OCT-3. There are two major classes of such variants: active allelic variants, naturally occurring variants of SEQ ID NOs:2 and 4 that have the ability to act as a transporter and non-active allelic variants, naturally occurring allelic variants of SEQ ID NOs:2 and 4 that are unable to function as a transporter. Active allelic variants can be used as an equivalent for an OCT-3 protein having the amino acid sequence of SEQ ID NOs:2 or 4 as described herein whereas nonactive allelic variants can be used in methods of disease diagnosis and as a therapeutic target.

[0039] The invention features methods of detecting and isolating such nucleic acid molecules. Using these methods, a sample (e.g., a nucleic acid library, such as a cDNA or genomic library) is contacted (or “screened”) with an oct-3-specific probe (e.g., a fragment of SEQ ID NO:1 or 3 that is at least 17 nucleotides long). The probe will selectively hybridize to nucleic acids encoding related polypeptides (or to complementary sequences thereof). The term “selectively hybridize” is used to refer to an event in which a probe binds to nucleic acid molecules encoding OCT-3 (or to complementary sequences thereof) to a detectably greater extent than to nucleic acids encoding other polypeptides, particularly other types of transporter molecules (or to complementary sequences thereof). The probe, which can contain at least 17 nucleotides (e.g., 18, 20, 25, 50, 100, 150, or 200 nucleotides) can be produced using any of several standard methods (see, e.g., Ausubel et al., “Current Protocols in Molecular Biology, Vol. I,” Green Publishing Associates, Inc., and John Wiley & Sons, Inc., NY, 1989). For example, the probe can be generated using PCR amplification methods in which oligonucleotide primers are used to amplify an oct-3-specific nucleic acid sequence (for example, a nucleic acid encoding one of the transmembrane domains) that can be used as a probe to screen a nucleic acid library and thereby detect nucleic acid molecules (within the library) that hybridize to the probe.

[0040] One single-stranded nucleic acid is said to hybridize to another if a duplex forms between them. This occurs when one nucleic acid contains a sequence that is the reverse and complement of the other (this same arrangement gives rise to the natural interaction between the sense and antisense strands of DNA in the genome and underlies the configuration of the double helix). Complete complementarity between the hybridizing regions is not required in order for a duplex to form; it is only necessary that the number of paired bases is sufficient to maintain the duplex under the hybridization conditions used.

[0041] Typically, hybridization conditions initially used to identify related genes are of low to moderate stringency. These conditions favor specific interactions between completely complementary sequences, but allow some non-specific interaction between less than perfectly matched sequences to occur as well. After hybridization, the nucleic acids can be “washed” under moderate or high conditions of stringency to dissociate duplexes that are bound together by some non-specific interaction (the nucleic acids that form these duplexes are thus not completely complementary).

[0042] As is known in the art, the optimal conditions for washing are determined empirically, often by gradually increasing the stringency. The parameters that can be changed to affect stringency include, primarily, temperature and salt concentration. In general, the lower the salt concentration and the higher the temperature, the higher the stringency. Washing can be initiated at a low temperature (e.g., room temperature) using a solution containing a salt concentration that is equivalent to or lower than that of the hybridization solution. Subsequent washing can be carried out using progressively warmer solutions having the same salt concentration. As alternatives, the salt concentration can be lowered and the temperature maintained in the washing step, or the salt concentration can be lowered and the temperature increased. Additional parameters can also be altered. For example, use of a destabilizing agent, such as formamide, alters the stringency conditions.

[0043] In reactions where nucleic acids are hybridized, the conditions used to achieve a given level of stringency will vary. There is not one set of conditions, for example, that will allow duplexes to form between all nucleic acids that are 85% identical to one another; hybridization also depends on unique features of each nucleic acid. The length of the sequence, the composition of the sequence (e.g., the content of purine-like nucleotides versus the content of pyrimidine-like nucleotides) and the type of nucleic acid (e.g., DNA or RNA) affect hybridization. An additional consideration is whether one of the nucleic acids is immobilized (e.g., on a filter).

[0044] An example of a progression from lower to higher stringency conditions is the following, where the salt content is given as the relative abundance of SSC (a salt solution containing sodium chloride and sodium citrate; 2×SSC is 10-fold more concentrated than 0.2×SSC). Nucleic acid molecules are hybridized at 42° C. in 2×SSC/0.1% SDS (sodium dodecylsulfate, a detergent) and then washed in 0.2×SSC/0.1% SDS at room temperature (for conditions of low stringency); 0.2×SSC/0.1% SDS at 42° C. (for conditions of moderate stringency); and 0.1×SSC at 68° C. (for conditions of high stringency). Washing can be carried out using only one of the conditions given, or each of the conditions can be used (for example, washing for 10-15 minutes each in the order listed above). Any or all of the washes can be repeated. As mentioned above, optimal conditions will vary and can be determined empirically.

[0045] A second set of conditions that are considered “stringent conditions” are those in which hybridization is carried out at 50° C. in Church buffer (7% SDS, 0.5% NaHPO4, 1 M EDTA, 1% BSA) and washing is carried out at 50° C. in 2×SSC.

[0046] Preferably, nucleic acid molecules of the invention that are defined by their ability to hybridize with SEQ ID NOs: 1, 3, or 5, or a complement thereof under stringent conditions will have additional features in common with oct-3. For example, the nucleic acid molecules identified by hybridization may have a similar, or identical, expression profile as the oct-3 molecules described herein, or may encode a polypeptide having one or more of the biological activities possessed by OCT-3.

[0047] Once detected, the nucleic acid molecules can be isolated by any of a number of standard techniques (see, e.g., Sambrook et al., “Molecular Cloning, A Laboratory Manual,” 2nd Ed. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989).

[0048] The invention also encompasses: (a) expression vectors that contain any of the foregoing oct-3 or oct-3-related coding sequences and/or their complements (i.e., “antisense” sequence) and fragments thereof; (b) expression vectors that contain any of the foregoing oct-3-related sequences operatively associated with a regulatory element (examples of which are given below) that directs the expression of the coding sequences; (c) expression vectors containing, in addition to sequences encoding an OCT-3 polypeptide, nucleic acid sequences that are unrelated to nucleic acid sequences encoding OCT-3, such as molecules encoding a reporter or marker; and (d) genetically engineered host cells that contain any of the foregoing expression vectors, and thereby express the nucleic acid molecules of the invention in the host cell. The regulatory elements referred to above include, but are not limited to, inducible and non-inducible promoters, enhancers, operators and other elements, which are known to those skilled in the art, and which drive or otherwise regulate gene expression. Such regulatory elements include but are not limited to the cytomegalovirus hCMV immediate early gene, the early or late promoters of SV40 adenovirus, the lac system, the trp system, the TAC system, the TRC system, the major operator and promoter regions of phage &lgr;, the control regions of fd coat protein, the promoter for 3-phosphoglycerate kinase, the promoters of acid phosphatase, and the promoters of the yeast &agr;-mating factors.

[0049] Additionally, the OCT-3 encoding nucleic acid molecules of the present invention can form part of a hybrid gene encoding additional polypeptide sequences, for example, sequences that function as a marker or reporter. Examples of marker or reporter genes include &bgr;-lactamase, chloramphenicol acetyltransferase (CAT), adenosine deaminase (ADA), aminoglycoside phosphotransferase (neor, G418r), dihydrofolate reductase (DHFR), hygromycin-B-phosphotransferase (HPH), thymidine kinase (TK), lacZ (encoding &bgr;-galactosidase), and xanthine guanine phosphoribosyltransferase (XGPRT). As with many of the standard procedures associated with the practice of the invention, skilled artisans will be aware of additional useful reagents, for example, of additional sequences that can serve the function of a marker or reporter. Generally, a chimeric or hybrid polypeptide of the invention will include a first portion and a second portion; the first portion being an OCT-3 polypeptide or a fragment thereof (preferably a biologically active fragment) and the second portion being, for example, the reporter described above or an immunoglobulin constant region.

[0050] The expression systems that can be used for purposes of the invention include, but are not limited to, microorganisms such as bacteria (e.g., E. coli and B. subtilis) transformed with recombinant bacteriophage DNA, plasmid DNA, or cosmid DNA expression vectors containing the nucleic acid molecules of the invention; yeast (e.g., Saccharomyces and Pichia) transformed with recombinant yeast expression vectors containing the nucleic acid molecules of the invention (preferably containing a nucleic acid sequence encoding OCT-3, such as the sequence of SEQ ID NOs: 1, 3, or 5); insect cell systems infected with recombinant virus expression vectors (e.g., baculovirus) containing a nucleic acid molecule of the invention; plant cell systems infected with recombinant virus expression vectors (e.g., cauliflower mosaic virus (CaMV) and tobacco mosaic virus (TMV)) or transformed with recombinant plasmid expression vectors (e.g., Ti plasmid) containing oct-3 nucleotide sequences; or mammalian cell systems (e.g., COS, CHO, BHK, 293, VERO, HeLa, MDCK, WI38, and NIH 3T3 cells) harboring recombinant expression constructs containing promoters derived from the genome of mammalian cells (e.g., the metallothionein promoter) or from mammalian viruses (e.g., the adenovirus late promoter and the vaccinia virus 7.5K promoter).

[0051] In bacterial systems, a number of expression vectors may be advantageously selected depending upon the use intended for the gene product being expressed. For example, when a large quantity of such a protein is to be produced, for the generation of pharmaceutical compositions containing OCT-3 polypeptides or for raising antibodies to those polypeptides, vectors that are capable of directing the expression of high levels of fusion protein products that are readily purified may be desirable. Such vectors include, but are not limited to, the E. coli expression vector pUR278 (Ruther et al., EMBO J. 2:1791, 1983), in which the coding sequence of the insert may be ligated individually into the vector in frame with the lacZ coding region so that a fusion protein is produced; pIN vectors (Inouye and Inouye, Nucleic Acids Res. 13:3101-3109, 1985; Van Heeke and Schuster, J. Biol. Chem. 264:5503-5509, 1989); and the like. pGEX vectors may also be used to express foreign polypeptides as fusion proteins with glutathione S-transferase (GST). In general, such fusion proteins are soluble and can easily be purified from lysed cells by adsorption to glutathione-agarose beads followed by elution in the presence of free glutathione. The pGEX vectors are designed to include thrombin or factor Xa protease cleavage sites so that the cloned target gene product can be released from the GST moiety.

[0052] In an insect system, Autographa californica nuclear polyhidrosis virus (AcNPV) can be used as a vector to express foreign genes. The virus grows in Spodoptera frugiperda cells. The coding sequence of the insert may be cloned individually into non-essential regions (e.g., the polyhedrin gene) of the virus and placed under control of an AcNPV promoter (e.g., the polyhedrin promoter). Successful insertion of the coding sequence will result in inactivation of the polyhedrin gene and production of non-occluded recombinant virus (i.e., virus lacking the proteinaceous coat coded for by the polyhedrin gene). These recombinant viruses are then used to infect Spodoptera frugiperda cells in which the inserted gene is expressed (e.g., see Smith et al., J. Virol. 46:584, 1983; and Smith, U.S. Pat. No. 4,215,051).

[0053] In mammalian host cells, a number of viral-based expression systems may be utilized. In cases where an adenovirus is used as an expression vector, the nucleic acid molecule of the invention can be ligated to an adenovirus transcription/translation control complex, for example, the late promoter and tripartite leader sequence. This chimeric gene may then be inserted in the adenovirus genome by in vitro or in vivo recombination. Insertion in a non-essential region of the viral genome (e.g., region E1 or E3) will result in a recombinant virus that is viable and capable of expressing an oct-3 gene product in infected hosts (e.g., see Logan and Shenk, Proc. Natl. Acad. Sci. USA 81:3655-3659, 1984). Specific initiation signals may also be required for efficient translation of inserted nucleic acid molecules. These signals include the ATG initiation codon and adjacent sequences. In cases where an entire gene or cDNA, including its own initiation codon and adjacent sequences, is inserted into the appropriate expression vector, no additional translational control signals may be needed. However, in cases where only a portion of the coding sequence is inserted (e.g., the portion encoding the mature form of an OCT-3 protein) endoexogenous translational control signals, including, perhaps, the ATG initiation codon, must be provided. Furthermore, the initiation codon must be in phase with the reading frame of the desired coding sequence to ensure translation of the entire insert. These exogenous translational control signals and initiation codons can be of a variety of origins, both natural and synthetic. The efficiency of expression may be enhanced by the inclusion of appropriate transcription enhancer elements, transcription terminators, etc. (see Bittner et al., Methods in Enzymol. 153:516-544, 1987).

[0054] In addition, a host cell strain may be chosen that modulates the expression of the inserted sequences, or modifies and processes the gene product in the specific fashion desired. Such modifications (e.g., glycosylation) and processing (e.g., cleavage) of protein products may be important for the function of the protein. Different host cells have characteristic and specific mechanisms for the post-translational processing and modification of proteins and gene products. Appropriate cell lines or host systems can be chosen to ensure the correct modification and processing of the foreign protein expressed. To this end, eukaryotic host cells that possess the cellular machinery for proper processing of the primary transcript, glycosylation, and phosphorylation of the gene product can be used. The mammalian cell types listed above are among those that could serve as suitable host cells.

[0055] For long-term, high-yield production of recombinant proteins, stable expression is preferred. For example, cell lines which stably express the OCT-3 sequences described above can be engineered. Rather than using expression vectors that contain viral origins of replication, host cells can be transformed with DNA controlled by appropriate expression control elements (e.g., promoter sequences, enhancer sequences, transcription terminators, polyadenylation sites, etc.), and a selectable marker. Following the introduction of the foreign DNA, engineered cells can be allowed to grow for 1-2 days in an enriched media, and then switched to a selective media. The selectable marker in the recombinant plasmid confers resistance to the selection, and allows cells to stably integrate the plasmid into their chromosomes and grow to form foci which, in turn, can be cloned and expanded into cell lines. This method can advantageously be used to engineer cell lines that express OCT-3. Such engineered cell lines may be particularly useful in screening and evaluating compounds that affect the endogenous activity of the gene product (i.e., OCT-3).

[0056] A number of selection systems can be used. For example, the herpes simplex virus thymidine kinase (Wigler, et al., Cell 11:223, 1977), hypoxanthine-guanine phosphoribosyltransferase (Szybalska and Szybalski, Proc. Natl. Acad. Sci. USA 48:2026, 1962), and adenine phosphoribosyltransferase (Lowy, et al., Cell 22:817, 1980) genes can be employed in tk−, hgprt− or aprt− cells, respectively. Also, anti-metabolite resistance can be used as the basis of selection for the following genes: dhfr, which confers resistance to methotrexate (Wigler et al., Proc. Natl. Acad. Sci. USA 77:3567, 1980; O'Hare et al., Proc. Natl. Acad. Sci. USA 78:1527, 1981); gpt, which confers resistance to mycophenolic acid (Mulligan and Berg, Proc. Natl. Acad. Sci. USA 78:2072, 1981); neo, which confers resistance to the aminoglycoside G-418 (Colberre-Garapin et al., J. Mol. Biol. 150:1, 1981); and hygro, which confers resistance to hygromycin (Santerre et al., Gene 30:147, 1984).

[0057] Alternatively, any OCT-3-containing fusion protein can be readily purified by utilizing an antibody specific for the fusion protein being expressed. For example, a system described by Janknecht et al. allows for the ready purification of non-denatured fusion proteins expressed in human cell lines (Proc. Natl. Acad. Sci. USA 88:8972-8976, 1991). In this system, the gene of interest is subcloned into a vaccinia recombination plasmid such that the gene's open reading frame is translationally fused to an amino-terminal tag consisting of six histidine residues. Extracts from cells infected with recombinant vaccinia virus are loaded onto Ni2+-nitriloacetic acid-agarose columns and histidine-tagged proteins are selectively eluted with imidazole-containing buffers.

[0058] As implied by the descriptions above, a host cell is any cell into which (or into an ancestor of which) a nucleic acid encoding a polypeptide of the invention (e.g., an OCT-3 polypeptide) has been introduced by means of recombinant DNA techniques.

[0059] OCT-3 Polypeptides

[0060] The OCT-3 polypeptides described herein are those encoded by any of the nucleic acid molecules described above, and include fragments of OCT-3, mutant forms of OCT-3, active and non-active allelic variants of OCT-3, splice variants of OCT-3, truncated forms of OCT-3, and fusion proteins containing all or a portion of OCT-3. These polypeptides can be prepared for a variety of uses including, but not limited to, the generation of antibodies, as reagents in diagnostic assays, for the identification of other cellular gene products or exogenous compounds that can modulate the activity or expression of OCT-3, and as pharmaceutical reagents useful for the treatment of any disorder in which the associated symptoms are improved by altering the activity of OCT-3.

[0061] The terms “protein” and “polypeptide” are used herein to describe any chain of amino acid residues, regardless of length or post-translational modification (e.g., modification by glycosylation or phosphorylation). Thus, the term “OCT-3 polypeptide” includes full-length, naturally occurring OCT-3 polypeptides (that can be purified from tissues in which they are naturally expressed, according to standard biochemical methods of purification), as well as recombinantly or synthetically produced polypeptides that correspond either to a full-length, naturally-occurring OCT-3 polypeptide or to particular domains or portions of such a polypeptide. The term also encompasses mature OCT-3 having an added amino-terminal methionine (useful for expression in prokaryotic cells).

[0062] Preferred polypeptides are substantially pure OCT-3 polypeptides that are at least 50% (e.g., 55%, 60%, or 65%), more preferably at least 70% (e.g., 72%, 75%, or 78%), even more preferably at least 80% (e.g., 80%, 85% or 90%), and most preferably at least 95% (e.g., 97% or even 99%) identical to SEQ ID NOs:2, 4, or 6. Those of ordinary skill in the art are well able to determine the percent identity between two amino acid sequences. Further guidance on this point is provided above. In addition, in FIGS. 4A-4E, regions of amino acid sequence that, along with the TM domains, are conserved between OCT-3 and other members of the OCT family of proteins (OCT-1 and OCT-2) are shown. Thus, if a polypeptide is encoded by a nucleic acid that hybridizes under stringent conditions with the oct-3 sequence disclosed herein and also encodes one or more of the conserved regions present in OCT-3, it will be recognized as an OCT-3 polypeptide and thereby considered within the scope of the present invention.

[0063] The invention also encompasses polypeptides that are functionally equivalent to OCT-3. These polypeptides are equivalent to OCT-3 in that they are capable of carrying out one or more of the functions of OCT-3 in a biological system. Polypeptides that are functionally equivalent to OCT-3 can have 20%, 40%, 50%, 75%, 80%, or even 90% of one or more of the biological activities of the full-length, mature human form of OCT-3. Such comparisons are generally based on an assay of biological activity in which equal concentrations of the polypeptides (i.e., an OCT-3 polypeptide disclosed herein and a candidate OCT-3 polypeptide) are used and compared. The comparison can also be based on the amount of the polypeptide required to reach 50% of the maximal biological activity obtainable.

[0064] Functionally equivalent proteins can be those, for example, that contain additional or substituted amino acid residues. Substitutions may be made on the basis of similarity in polarity, charge, solubility, hydrophobicity, hydrophilicity, and/or the amphipathic nature of the residues involved. Amino acids that are typically considered to provide a conservative substitution for one another are specified in the

SUMMARY OF THE INVENTION

[0065] Polypeptides that are functionally equivalent to OCT-3 (e.g., SEQ ID NO:2, 4, or 6) can be made using random mutagenesis techniques well known to those of ordinary skill in the art (and the resulting mutant OCT-3 polypeptides can be tested for activity). It is more likely, however, that such polypeptides will be generated by site-directed mutagenesis (again using techniques well known to persons of ordinary skill in the art). These polypeptides may have increased functionality or decreased functionality.

[0066] To design functionally equivalent polypeptides, it is useful to distinguish between conserved positions and variable positions. This can be done by aligning the sequence of oct-3 cDNAs that were obtained from various organisms. Skilled artisans will recognize that conserved amino acid residues are more likely to be necessary for preservation of function. Thus, it is preferable that conserved residues are not altered.

[0067] Mutations within the oct-3 coding sequence can be made to generate variant oct-3 genes that are better suited for expression in a selected host cell. For example, N-linked glycosylation sites can be altered or eliminated to achieve, for example, expression of a homogeneous product that is more easily recovered and purified from yeast hosts which are known to hyperglycosylate N-linked sites. To this end, a variety of amino acid substitutions at one or both of the first or third amino acid positions of any one or more of the glycosylation recognition sequences which occur (in N—X—S or N—X—), and/or an amino acid deletion at the second position of any one or more of such recognition sequences, will prevent glycosylation at the modified tripeptide sequence (see, e.g., Miyajima et al., EMBO J. 5:1193, 1986).

[0068] The polypeptides of the invention can be expressed fused to another polypeptide, for example, a marker polypeptide or fusion partner. For example, the polypeptide can be fused to a hexa-histidine tag to facilitate purification of bacterially expressed protein or a hemagglutinin tag to facilitate purification of protein expressed in eukaryotic cells. In addition, an OCT-3 polypeptide can be fused to GST.

[0069] The polypeptides of the invention can be chemically synthesized (e.g., see Creighton, “Proteins: Structures and Molecular Principles,” W. H. Freeman & Co., NY, 1983), or, perhaps more advantageously, produced by recombinant DNA technology as described herein. For additional guidance, persons of ordinary skill in the art may consult Ausubel et al. (supra), Sambrook et al. (“Molecular Cloning, A Laboratory Manual,” Cold Spring Harbor Press, Cold Spring Harbor, N.Y., 1989), and, particularly for examples of chemical synthesis, Gait, M. J. (“Oligonucleotide Synthesis,” IRL Press, Oxford, 1984).

[0070] The invention also features polypeptides that interact with OCT-3 (and the genes that encode them) and thereby alter the function or activity of OCT-3. Interacting polypeptides can be identified using methods known to those of ordinary skill in the art. One suitable method is the “two-hybrid system,” which detects protein interactions in vivo (Chien et al., Proc. Natl. Acad. Sci. USA, 88:9578, 1991). A kit for practicing this method is available from Clontech (Palo Alto, Calif.).

[0071] Transgenic Animals

[0072] OCT-3 polypeptides can also be expressed in transgenic animals. Such transgenic animals represent model systems for the study of disorders that are either caused by or exacerbated by misexpression of oct-3, or disorders that can be treated by altering the expression of oct-3 or the activity of OCT-3 (even though the expression or activity is not detectably abnormal). Transgenic animals can also be used for the development of therapeutic agents that modulate the expression of oct-3 or the activity of OCT-3.

[0073] Transgenic animals can be farm animals (e.g., pigs, goats, sheep, cows, horses, rabbits, and the like) rodents (such as rats, guinea pigs, and mice), non-human primates (e.g., baboons, monkeys, and chimpanzees), and domestic animals (e.g., dogs and cats). Transgenic mice are especially preferred.

[0074] Any technique known in the art can be used to introduce an oct-3 transgene into animals to produce founder lines of transgenic animals. Such techniques include, but are not limited to, pronuclear microinjection (U.S. Pat. No. 4,873,191); retrovirus mediated gene transfer into germ lines (Van der Putten et al., Proc. Natl. Acad. Sci., USA 82:6148, 1985); gene targeting into embryonic stem cells (Thompson et al., Cell 56:313, 1989); and electroporation of embryos (Lo, Mol. Cell. Biol. 3:1803, 1983).

[0075] The present invention provides for transgenic animals that carry an oct-3 transgene in all of their cells, as well as animals that carry a transgene in some, but not all of their cells. For example, the invention provides for mosaic animals. The oct-3 transgene can be integrated as a single transgene or in concatamers, for example, head-to-head tandems or head-to-tail tandems. The transgene can also be selectively introduced into, and activated in, a particular cell type (Lasko et al., Proc. Natl. Acad. Sci. USA 89:6232, 1992). The regulatory sequences required for such a cell-type specific activation will depend upon the particular cell type of interest, and will be apparent to those of skill in the art.

[0076] When it is desired that an oct-3 transgene be integrated into the chromosomal site of an endogenous oct-3 gene, gene targeting is preferred. Briefly, when such a technique is to be used, vectors containing some nucleotide sequences homologous to an endogenous oct-3 gene are designed for the purpose of integrating, via homologous recombination with chromosomal sequences, into and disrupting the function of the nucleotide sequence of the endogenous gene. The transgene also can be selectively introduced into a particular cell type, thus inactivating the endogenous oct-3 gene in only that cell type (Gu et al., Science 265:103, 1984). The regulatory sequences required for such a cell-type specific inactivation will depend upon the particular cell type of interest, and will be apparent to those of skill in the art. These techniques are useful for preparing “knock outs” having no functional oct-3 gene.

[0077] Once transgenic animals have been generated, the expression of the recombinant oct-3 gene can be assayed utilizing standard techniques. Initial screening may be accomplished by Southern blot analysis or PCR techniques to determine whether integration of the transgene has taken place. The level of mRNA expression of the transgene in the tissues of the transgenic animals may also be assessed using techniques which include, but are not limited to, Northern blot analysis of tissue samples obtained from the animal, in situ hybridization analysis, and RT-PCR. Samples of oct-3 gene-expressing tissue can also be evaluated immunocytochemically using antibodies specific for the OCT-3 transgene product.

[0078] For a review of techniques that can be used to generate and assess transgenic animals, those of ordinary skill in the art can consult Gordon (Intl. Rev. Cytol. 115:171-229, 1989), and may obtain additional guidance from, for example: Hogan et al. “Manipulating the Mouse Embryo” (Cold Spring Harbor Press, Cold Spring Harbor, N.Y., 1986; Krimpenfort et al., Bio/Technology 9:86, 1991; Palmiter et al., Cell 41:343, 1985; Kraemer et al., “Genetic Manipulation of the Early Mammalian Embryo,” Cold Spring Harbor Press, Cold Spring Harbor, N.Y., 1985; Hammer et al., Nature 315:680, 1985; Purcel et al., Science 244:1281, 1986; Wagner et al., U.S. Pat. No. 5,175,385; and Krimpenfort et al., U.S. Pat. No. 5,175,384.

[0079] The transgenic animals of the invention can be used to determine the consequence of altering the expression of oct-3 in the context of various disease states. For example, oct-3 knock out mice can be generated using an established line of mice that serve as a model for a neurodegenerative disease. For example, oct-3 can be knocked out in mice bearing a mutation in the weaver gene, which allows them to serve as a model for Parkinson's Disease. If the symptoms (e.g., altered balance or gait) normally apparent in weaver mice are lessened when an oct-3 gene is no longer expressed, patients suffering from Parkinson's Disease are likely to benefit from treatment with any compound that decreases the expression of oct-3 or the activity of OCT-3.

[0080] Anti-OCT-3 Antibodies

[0081] OCT-3 polypeptides (or immunogenic fragments or analogs thereof) can be used to raise antibodies useful in the invention; such polypeptides can be produced by recombinant techniques or synthesized (see, for example, “Solid Phase Peptide Synthesis,” supra; Ausubel et al., supra). In general, OCT-3 polypeptides can be coupled to a carrier protein, such as KLH (keyhole limpet hemocyanin), as described in Ausubel et al., supra, mixed with an adjuvant, and injected into a host mammal. Antibodies produced in that animal can then be purified by peptide antigen affinity chromatography.

[0082] In particular, various host animals can be immunized by injection with a OCT-3 polypeptide, or an antigenic fragment thereof. Commonly employed host animals include rabbits, mice, guinea pigs, and rats. Various adjuvants that can be used to increase the immunological response depend on the host species and include Freund's adjuvant (complete and incomplete), mineral gels such as aluminum hydroxide, surface active substances such as lysolecithin, pluronic polyols, polyanions, peptides, oil emulsions, KLH, and dinitrophenol. Potentially useful human adjuvants include BCG (bacille Calmette-Guerin) and Corynebacterium parvum. Polyclonal antibodies are heterogeneous populations of antibody molecules that are contained in the sera of the immunized animals.

[0083] Antibodies within the invention therefore include polyclonal antibodies and, in addition, monoclonal antibodies, humanized or chimeric antibodies, single chain antibodies, Fab fragments, F(ab′)2 fragments, and molecules produced using a Fab expression library.

[0084] Monoclonal antibodies, which are homogeneous populations of antibodies to a particular antigen, can be prepared using the OCT-3 polypeptides described above and standard hybridoma technology (see, for example, Kohler et al., Nature 256:495, 1975; Kohler et al., Eur. J. Immunol. 6:511, 1976; Kohler et al., Eur. J. Immunol. 6:292, 1976; Hammerling et al., “Monoclonal Antibodies and T Cell Hybridomas,” Elsevier, N.Y., 1981; Ausubel et al., supra).

[0085] In particular, monoclonal antibodies can be obtained by any technique that provides for the production of antibody molecules by continuous cell lines in culture such as described in Kohler et al., Nature 256:495, 1975, and U.S. Pat. No. 4,376,110; the human B-cell hybridoma technique (Kosbor et al., Immunology Today 4:72, 1983; Cole et al., Proc. Natl. Acad. Sci. USA 80:2026, 1983), and the EBV-hybridoma technique (Cole et al., “Monoclonal Antibodies and Cancer Therapy,” Alan R. Liss, Inc., pp. 77-96, 1983). Such antibodies can be of any immunoglobulin class including IgG, IgM, IgE, IgA, IgD and any subclass thereof. The hybridoma producing the mAb of this invention may be cultivated in vitro or in vivo. The ability to produce high titers of mAbs in vivo makes this a particularly useful method of production.

[0086] Once produced, polyclonal or monoclonal antibodies are tested for specific OCT-3 recognition by Western blot or immunoprecipitation analysis by standard methods, for example, as described in Ausubel et al., supra. Antibodies that specifically recognize and bind to OCT-3 are useful in the invention. For example, such antibodies can be used in an immunoassay to monitor the level of OCT-3 produced by a mammal (e.g., to determine the amount or subcellular location of OCT-3).

[0087] There are two major classes of antibodies which are within the scope of the present invention. The first class are antibodies that selectively bind to OCT-3 polypeptide, not bind to other members of the OCT family of proteins. The second class are antibodies that bind to more than one member of the OCT family of proteins.

[0088] Preferably, OCT-3 selective antibodies of the invention are produced using fragments of the OCT-3 polypeptide that lie outside highly conserved regions (such as the TM domains and the regions shown in FIGS. 4A-4E) and appear likely to be antigenic, by criteria such as high frequency of charged residues. Cross-reactive anti-OCT-3 antibodies are produced using a fragment of OCT-3 that is conserved amoungst members of this family of proteins. In one specific example, such fragments are generated by standard techniques of PCR, and are then cloned into the pGEX expression vector (Ausubel et al., supra). Fusion proteins are expressed in E. coli and purified using a glutathione agarose affinity matrix as described in Ausubel, et al., supra.

[0089] In some cases it may be desirable to minimize the potential problems of low affinity or specificity of antisera. In such circumstances, two or three fusions can be generated for each protein, and each fusion can be injected into at least two rabbits. Antisera can be raised by injections in a series, preferably including at least three booster injections.

[0090] Antiserum is also checked for its ability to immunoprecipitate recombinant OCT-3 polypeptides or control proteins, such as glucocorticoid receptor, CAT, or luciferase.

[0091] The antibodies can be used, for example, in the detection of OCT-3 in a biological sample as part of a diagnostic assay or to reduce OCT-3 activity as part of a theraputic regime (e.g., to reduce an undesirably high level of OCT-3 activity). Antibodies also can be used in a screening assay to measure the effect of a candidate compound on expression or localization of OCT-3. Additionally, such antibodies can be used in conjunction with the gene therapy techniques. For example, they may be used to evaluate the normal and/or engineered OCT-3-expressing cells prior to their introduction into the patient.

[0092] In addition, techniques developed for the production of “chimeric antibodies” (Morrison et al., Proc. Natl. Acad. Sci. USA 81:6851, 1984; Neuberger et al., Nature 312:604, 1984; Takeda et al., Nature 314:452, 1984) by splicing the genes from a mouse antibody molecule of appropriate antigen specificity together with genes from a human antibody molecule of appropriate biological activity can be used. A chimeric antibody is a molecule in which different portions are derived from different animal species, such as those having a variable region derived from a murine mAb and a human immunoglobulin constant region.

[0093] Alternatively, techniques described for the production of single chain antibodies (U.S. Pat. Nos. 4,946,778, 4,946,778, and 4,704,692) can be adapted to produce single chain antibodies against an OCT-3 polypeptide, or a fragment thereof. Single chain antibodies are formed by linking the heavy and light chain fragments of the Fv region via an amino acid bridge, resulting in a single chain polypeptide.

[0094] Antibody fragments that recognize and bind to specific epitopes can be generated by known techniques. For example, such fragments include but are not limited to F(ab′)2 fragments that can be produced by pepsin digestion of the antibody molecule, and Fab fragments that can be generated by reducing the disulfide bridges of F(ab′)2 fragments. Alternatively, Fab expression libraries can be constructed (Huse et al., Science 246:1275, 1989) to allow rapid and easy identification of monoclonal Fab fragments with the desired specificity.

[0095] Antibodies can be humanized by methods known in the art. For example, monoclonal antibodies with a desired binding specificity can be commercially humanized (Scotgene, Scotland; Oxford Molecular, Palo Alto, Calif.). Fully human antibodies, such as those expressed in transgenic animals are also features of the invention (Green et al., Nature Genetics 7:13-21, 1994; see also U.S. Pat. Nos. 5,545,806 and 5,569,825).

[0096] The methods described herein, in which anti-OCT-3 antibodies are employed, can be performed, for example, by utilizing pre-packaged diagnostic kits comprising at least one specific oct-3 nucleotide sequence or antibody reagent described herein, which may be conveniently used, for example, in clinical settings, to diagnose patients exhibiting symptoms of the disorders described below.

[0097] Antisense Nucleic Acid Molecules

[0098] Treatment regimes based on an “antisense” approach involve the design of oligonucleotides (either DNA or RNA) that are complementary to a portion of a selected mRNA. These oligonucleotides bind to complementary mRNA transcripts and prevent their translation. Absolute complementarity, although preferred, is not required. A sequence “complementary” to a portion of an RNA molecule, as referred to herein, is a sequence having sufficient complementarily to hybridize with the RNA, forming a stable duplex; in the case of double-stranded antisense nucleic acids, a single strand of the duplex DNA can be tested, or triplex formation can be assayed. The ability to hybridize will depend on both the degree of complementarily and the length of the antisense nucleic acid. Generally, the longer the hybridizing nucleic acid, the more base mismatches with an RNA it may contain and still form a stable duplex (or triplex, as the case may be). One of ordinary skill in the art can ascertain a tolerable degree of mismatch by use of standard procedures to determine the melting point of the hybridized complex.

[0099] Oligonucleotides that are complementary to the 5′ end of the message, for example, the 5′ untranslated sequence up to and including the AUG initiation codon, should work most efficiently at inhibiting translation. However, sequences complementary to the 3′ untranslated sequences of mRNAs recently have been shown to be effective at inhibiting translation of mRNAs as well (Wagner, Nature 372:333, 1984). Thus, oligonucleotides complementary to either the 5′ or 3′ non-translated, non-coding regions of an oct-3 gene, for example, a human gene as shown in FIGS. 1A-1C or FIGS. 2A-2B, could be used in an antisense approach to inhibit translation of endogenous oct-3 mRNA. Oligonucleotides complementary to the 5′ untranslated region of the mRNA should include the complement of the AUG start codon.

[0100] Antisense oligonucleotides complementary to mRNA coding regions are less efficient inhibitors of translation but could be used in accordance with the invention. Whether designed to hybridize to the 5′, 3′, or coding region of oct-3 mRNA, antisense nucleic acids should be at least six nucleotides in length, and are preferably oligonucleotides ranging from 6 to about 50 nucleotides in length. In specific aspects, the oligonucleotide is at least 10 nucleotides, at least 17 nucleotides, at least 25 nucleotides, or at least 50 nucleotides.

[0101] Regardless of the choice of target sequence, as with other therapeutic strategies directed to OCT-3, it is preferred that in vitro studies are first performed to assess the ability of an antisense oligonucleotide to inhibit gene expression. If desired, the assessment can be quantitative. It is preferred that these studies utilize controls that distinguish between antisense gene inhibition and any nonspecific biological effect that an oligonucleotide may incur. It is also preferred that these studies compare levels of the target RNA or protein with that of an internal control RNA or protein. Additionally, it is envisioned that results obtained using an antisense oligonucleotide are compared with those obtained using a control oligonucleotide. Preferably, the control oligonucleotide is of approximately the same length as the test oligonucleotide, and the nucleotide sequence of the control oligonucleotide differs from that of the test antisense sequence no more than is necessary to prevent specific hybridization between the control oligonucleotide and the targeted RNA sequence.

[0102] The oligonucleotides can contain DNA or RNA, or they can contain chimeric mixtures, derivatives, or modified versions thereof that are either single-stranded or double-stranded. The oligonucleotide can be modified at the base moiety, sugar moiety, or phosphate backbone, for example, to improve stability of the molecule, hybridization, etc. Modified sugar moieties can be selected from the group including, but not limited to, arabinose, 2-fluoroarabinose, xylulose, and hexose. A modified phosphate backbone can be selected from the group consisting of a phosphorothioate, a phosphorodithioate, a phosphoramidothioate, a phosphoramidate, a phosphordiamidate, a methylphosphonate, an alkyl phosphotriester, and a iformacetal, or an analog of any of these backbones.

[0103] The oligonucleotide can include other appended groups such as peptides (e.g., for disrupting the transport properties of the molecule in host cells in vivo), or agents that facilitate transport across the cell membrane (as described, for example, in Letsinger et al., Proc. Natl. Acad. Sci. USA 86:6553, 1989; Lemaitre et al., Proc. Natl. Acad. Sci. USA 84:648, 1987; PCT Publication No. WO 88/09810) or the blood-brain barrier (see, for example, PCT Publication No. WO 89/10134), or hybridization-triggered cleavage agents (see, for example, Krol et al., BioTechniques 6:958, 1988), or intercalating agents (see, for example, Zon, Pharm. Res. 5:539, 1988). To this end, the oligonucleotide can be conjugated to another molecule, for example, a peptide, a hybridization triggered cross-linking agent, a transport agent, or a hybridization-triggered cleavage agent.

[0104] An antisense oligonucleotide of the invention can comprise at least one modified base moiety that is selected from the group including, but not limited to, 5-fluoro-uracil, 5-bromouracil, 5-chlorouracil, 5-iodouracil, hypoxanthine, xantine, 4-acetylcytosine, 5-(carboxyhydroxyl-methyl) uracil, 5-carboxymethylaminomethyl-2-thiouridine, 5-carboxymethyl-aminomethyluracil, dihydrouracil, beta-D-galactosylqueosine, inosine, N6-isopentenyladenine, 1-methylguanine, 1-methylinosine, 2,2-dimethylguanine, 2-methyladenine, 2-methylguanine, 3-methylcytosine, 5-methylcytosine, N6-adenine, 7-methylguanine, 5-methyl-aminomethyluracil, 5-methoxyaminomethyl-2-thiouracil, beta-D-mannosylqueosine, 5′-methoxycarboxymethyluracil, 5-methoxyuracil, 2-methylthio-N6-isopentenyladenine, uracil-5-oxyacetic acid (v), wybutoxosine, pseudouracil, queosine, 2-thiocytosine, 5-methyl-2-theouracil, 2-thiouracil, 4-thio-uracil, 5-methyluracil, uracil-5-oxyacetic acid methylester, uracil-5-oxyacetic acid (v), 5-methyl-2-thiouracil, 2-(3-amino-3-N-2-carboxypropl) uracil, (acp3)w, and 2,6-diaminopurine.

[0105] In yet another embodiment, the antisense oligonucleotide is an &agr;-anomeric oligonucleotide. An &agr;-anomeric oligonucleotide forms specific double-stranded hybrids with complementary RNA in which, contrary to the usual &bgr;-units, the strands run parallel to each other (Gautier et al., Nucl. Acids. Res. 15:6625, 1987). The oligonucleotide is a 2′-0-methylribonucleotide (Inoue et al., Nucl. Acids Res. 15:6131, 1987), or a chimeric RNA-DNA analog (Inoue et al., FEBS Lett. 215:327, 1987).

[0106] Antisense oligonucleotides of the invention can be synthesized by standard methods known in the art, for example, by use of an automated DNA synthesizer (such as are commercially available from Biosearch, Applied Biosystems, etc.). As examples, phosphorothioate oligonucleotides can be synthesized by the method of Stein et al. (Nucl. Acids Res. 16:3209, 1988), and methylphosphonate oligonucleotides can be prepared by use of controlled pore glass polymer supports (Sarin et al., Proc. Natl. Acad. Sci. USA 85:7448, 1988).

[0107] While antisense oligonucleotides that are complementary to the coding region of oct-3 could be used, those complementary to the transcribed untranslated region are most preferred.

[0108] For therapeutic application, antisense molecules of the invention should be delivered to cells that express oct-3 in vivo. A number of methods have been developed for delivering antisense DNA or RNA to cells; for example, antisense molecules can be injected directly into the tissue site. Alternatively, modified antisense molecules, which are designed to target cells that express oct-3 (e.g., antisense molecules linked to peptides or antibodies that specifically bind receptors or antigens expressed on the target cell surface) can be administered systemically.

[0109] However, it is often difficult to achieve intracellular concentrations of antisense molecules that are sufficient to suppress translation of endogenous mRNAs. Therefore, a preferred approach uses a recombinant DNA construct in which the antisense oligonucleotide is placed under the control of a strong pol III or pol II promoter. The use of such a construct to transfect target cells in the patient will result in the transcription of sufficient amounts of single stranded RNAs that will form complementary base pairs with endogenous oct-3 transcripts and thereby prevent translation of oct-3 mRNA. For example, a vector can be introduced in vivo in such a way that it is taken up by a cell and thereafter directs the transcription of an antisense RNA. Such a vector can remain episomal or become chromosomally integrated, as long as it can be transcribed to produce the desired antisense RNA.

[0110] Vectors encoding an oct-3 antisense sequence can be constructed by recombinant DNA technology methods that are standard practice in the art. Suitable vectors include plasmid vectors, viral vectors, or other types of vectors known or newly discovered in the art. The criterion for use is only that the vector be capable of replicating and expressing the oct-3 antisense molecule in mammalian cells. Expression of the sequence encoding the antisense RNA can be directed by any promoter known in the art to act in mammalian, and preferably in human, cells. Such promoters can be inducible or constitutively active and include, but are not limited to: the SV40 early promoter region (Bernoist et al., Nature 290:304, 1981); the promoter contained in the 3′ long terminal repeat of Rous sarcoma virus (Yamamoto et al., Cell 22:787-797, 1988); the herpes thymidine kinase promoter (Wagner et al., Proc. Natl. Acad. Sci. USA 78:1441, 1981); or the regulatory sequences of the metallothionein gene (Brinster et al., Nature 296:39, 1988).

[0111] Ribozymes

[0112] Ribozyme molecules designed to catalytically cleave oct-3 mRNA transcripts also can be used to prevent translation of oct-3 mRNA and expression of OCT-3 polypeptides (see, for example, PCT Publication WO 90/11364; Saraver et al., Science 247:1222, 1990). While various ribozymes that cleave mRNA at site-specific recognition sequences can be used to destroy oct-3 mRNAs, the use of hammerhead ribozymes is preferred. Hammerhead ribozymes cleave mRNAs at locations dictated by flanking regions that form complementary base pairs with the target mRNA. The sole requirement is that the target mRNA have the following sequence of two bases: 5′-UG-3′. The construction and production of hammerhead ribozymes is well known in the art (Haseloff et al., Nature 334:585, 1988). There are numerous examples of potential hammerhead ribozyme cleavage sites within the nucleotide sequence of human oct-3 cDNA. Preferably, the ribozyme is engineered so that the cleavage recognition site is located near the 5′ end of the oct-3 mRNA, i.e., to increase efficiency and minimize the intracellular accumulation of non-functional mRNA transcripts.

[0113] The ribozymes of the present invention also include RNA endoribonucleases (hereinafter “Cech-type ribozymes”), such as the one that occurs naturally in Tetrahymena Thermophila (known as the IVS or L-19 IVS RNA), and which has been extensively described by Cech and his collaborators (Zaug et al., Science 224:574, 1984; Zaug et al., Science 231:470, 1986; Zug et al., Nature 324:429, 1986; PCT Application No. WO 88/04300; and Been et al., Cell 47:207, 1986). The Cech-type ribozymes have an eight base-pair sequence that hybridizes to a target RNA sequence, after which cleavage of the target RNA takes place. The invention encompasses those Cech-type ribozymes that target eight base-pair active site sequences present in oct-3.

[0114] As in the antisense approach, the ribozymes can be composed of modified oligonucleotides (e.g., for improved stability, targeting, etc.), and should be delivered to cells which express the oct-3 in vivo. A preferred method of delivery involves using a DNA construct “encoding” the ribozyme under the control of a strong constitutive pol III or pol II promoter, so that transfected cells will produce sufficient quantities of the ribozyme to destroy endogenous oct-3 messages and inhibit translation. Because ribozymes, unlike antisense molecules, are catalytic, a lower intracellular concentration is required for efficiency.

[0115] Peptide Nucleic Acids

[0116] Oct-3 nucleic acid molecules can be modified at the base moiety, sugar moiety, or phosphate backbone to improve, for example, the stability or solubility of the molecule or its ability to hybridize with other nucleic acid molecules. For example, the deoxyribose phosphate backbone of the nucleic acid can be modified to generate peptide nucleic acids (see Hyrup et al., Bioorganic Med. Chem. 4:5-23, 1996). As used herein, the terms “peptide nucleic acids” or “PNAs” refer to nucleic acid mimics, for example, DNA mimics, in which the deoxyribose phosphate backbone is replaced by a pseudopeptide backbone and only the four natural nucleobases are retained. The neutral backbone of PNAs has been shown to allow for specific hybridization to DNA and RNA under conditions of low ionic strength. The synthesis of PNA oligomers can be performed using standard solid phase peptide synthesis protocols as described in Hyrup et al., supra; Perry-O'Keefe et al. Proc. Natl. Acad. Sci. USA 93:14670-14675 (1996).

[0117] PNAs of oct-3 can be used in therapeutic and diagnostic applications. For example, PNAs can be used as antisense or antigene agents for sequence-specific modulation of gene expression by, for example, inducing transcription or translation arrest or inhibiting replication. PNAs of oct-3 can also be used, for example, in the analysis of single base pair mutations in a gene by, for example, PNA-directed PCR clamping; as artificial restriction enzymes when used in combination with other enzymes, for example, S1 nucleases (Hyrup et al., supra); or as probes or primers for DNA sequence and hybridization (Hyrup et al., supra; Perry-O'Keefe, supra).

[0118] In other embodiments, PNAs of oct-3 can be modified, for example, to enhance their stability or cellular uptake, by attaching lipophilic or other helper groups to the PNA, by the formation of PNA-DNA chimeras, or by the use of liposomes or other techniques of drug delivery known in the art. For example, PNA-DNA chimeras of oct-3 can be generated that may combine the advantageous properties of PNA and DNA. Such chimeras allow DNA recognition enzymes, for example, RNAse H and DNA polymerases, to interact with the DNA portion while the PNA portion would provide high binding affinity and specificity. PNA-DNA chimeras can be linked using linkers of appropriate lengths selected in terms of base stacking, number of bonds between the nucleobases, and orientation (Hyrup, supra). The synthesis of PNA-DNA chimeras can be performed as described in Hyrup, supra, and Finn et al., Nucl. Acids Res. 24:3357-3363 (1996). For example, a DNA chain can be synthesized on a solid support using standard phosphoramidite coupling chemistry and modified nucleoside analogs, e.g., 5′-(4-methoxytrityl)amino-5′-deoxy-thymidine phosphoramidite, can be used between the PNA and the 5′ end of DNA (Mag et al., Nucl. Acids Res. 17:5973-5988, 1989). PNA monomers are then coupled in a stepwise manner to produce a chimeric molecule with a 5′ PNA segment and a 3′ DNA segment (Finn et al., supra). Alternatively, chimeric molecules can be synthesized with a 5′ DNA segment and a 3′ PNA segment (Peterser et al., Bioorganic Med. Chem. Lett. 5:1119-11124 (1975).

[0119] In other embodiments, the oligonucleotide may include other appended groups such as peptides (e.g., for targeting host cell receptors in vivo), or agents facilitating transport across the cell membrane (see, e.g., Letsinger et al., Proc. Natl. Acad. Sci. USA 86:6553-6556 (1989); Lemaitre et al., Proc. Natl. Acad. Sci. USA 84:648-652 (1987); PCT Publication No. WO 88/09810, published Dec. 15, 1988) or the blood-brain barrier (see, e.g., PCT Publication No. WO 89/10134, published Apr. 25, 1988). In addition, oligonucleotides can be modified with hybridization-triggered cleavage agents (see, e.g., Krol et al., BioTech. 6:958-976 (1988)) or integrating agents (see, e.g., Zon, Pharm. Res. 5:539-549 (1988)). To this end, the oligonucleotide may be conjugated to another molecule, for example, a peptide, hybridization triggered corss-linking agent, transport agent, hybridization-triggered cleavage agent etc.

[0120] Proteins that Associate with OCT-3

[0121] The invention also features methods for identifying polypeptides that can associate with OCT-3, as well as the isolated interactor, for example, proteins that alter the ability of OCT-3 to transport molecules across the plasma membranes of cells in which it is expressed. Any method that is suitable for detecting protein-protein interactions can be employed to detect polypeptides that associate with OCT-3, whether these polypeptides associate with the transmembrane, intracellular, or extracellular domains of OCT-3. Among the traditional methods that can be employed are co-immuno-precipitation, crosslinking, and co-purification through gradients or chromatographic columns of cell lysates or proteins obtained from cell lysates and the use of OCT-3 to identify proteins in the lysate that interact with OCT-3. For these assays, the OCT-3 polypetide can be a full length OCT-3, an extracellular domain of OCT-3, or some other suitable OCT-3 polypeptide. Once isolated, such an interacting protein can be identified and cloned and then used, in conjunction with standard techniques, to alter the activity of the OCT-3 polypeptide with which it interacts. For example, at least a portion of the amino acid sequence of a protein that interacts with OCT-3 can be ascertained using techniques well known to those of skill in the art, such as via the Edman degradation technique. The amino acid sequence obtained can be used as a guide for the generation of oligonucleotide mixtures that can be used to screen for gene sequences encoding the interacting protein. Screening can be accomplished, for example, by standard hybridization or PCR techniques. Techniques for the generation of oligonucleotide mixtures and the screening are well-known (Ausubel, supra; and “PCR Protocols: A Guide to Methods and Applications,” Innis et al., eds. Academic Press, Inc., NY, 1990).

[0122] Additionally, methods can be employed that result directly in the identification of genes that encode proteins that interact with OCT-3. These methods include, for example, screening expression libraries, in a manner similar to the well known technique of antibody probing of &lgr;gt11 libraries, using labeled OCT-3 polypeptide or an OCT-3 fusion protein, for example, an OCT-3 polypeptide or domain fused to a marker such as an enzyme, fluorescent dye, a luminescent protein, or to an IgFc domain.

[0123] There are also methods available that can detect protein-protein interaction in vivo. A method which detects protein interactions in vivo is the two-hybrid system (Chien et al., Proc. Natl. Acad. Sci. USA 88:9578, 1991). A kit for practicing this method is available from Clontech (Palo Alto, Calif.).

[0124] Briefly, utilizing such a system, plasmids are constructed that encode two hybrid proteins: one plasmid includes a nucleotide sequence encoding the DNA-binding domain of a transcription activator protein fused to a nucleotide sequence encoding OCT-3, an OCT-3 polypeptide, or an OCT-3 fusion protein, and the other plasmid includes a nucleotide sequence encoding the transcription activator protein's activation domain fused to a cDNA encoding an unknown protein which has been recombined into this plasmid as part of a cDNA library. The DNA-binding domain fusion plasmid and the cDNA library are transformed into a strain of the yeast Saccharomyces cerevisiae that contains a reporter gene (e.g., HBS or LacZ) whose regulatory region contains the transcription activator's binding site. Either hybrid protein alone cannot activate transcription of the reporter gene: the DNA-binding domain hybrid cannot because it does not provide activation function, and the activation domain hybrid cannot because it cannot localize to the activator's binding sites. Interaction of the two hybrid proteins reconstitutes the functional activator protein and results in expression of the reporter gene, which is detected by an assay for the reporter gene product.

[0125] The two-hybrid system or related methodology can be used to screen activation domain libraries for proteins that interact with the “bait” gene product. By way of example, and not by way of limitation, OCT-3 may be used as the bait gene product. Total genomic or cDNA sequences are fused to the DNA encoding an activation domain. This library and a plasmid encoding a hybrid of bait OCT-3 gene product fused to the DNA-binding domain are cotransformed into a yeast reporter strain, and the resulting transformants are screened for those that express the reporter gene. For example, a bait oct-3 gene sequence, such as oct-3 or a fragment of oct-3 which encodes an OCT domain can be cloned into a vector such that it is translationally fused to the DNA encoding the DNA-binding domain of the GAL4 protein. These colonies are purified and the library plasmids responsible for reporter gene expression are isolated. DNA sequencing is then used to identify the proteins encoded by the library plasmids.

[0126] A cDNA library of the cell line from which proteins that interact with bait oct-3 gene product are to be detected can be made using methods routinely practiced in the art. According to the particular system described herein, for example, the cDNA fragments can be inserted into a vector such that they are translationally fused to the transcriptional activation domain of GALA. This library can be co-transformed along with the bait oct-3 gene-GAL4 fusion plasmid into a yeast strain which contains a lacZ gene driven by a promoter which contains GALA activation sequence. A cDNA encoded protein, fused to GALA transcriptional activation domain, that interacts with bait oct-3 gene product will reconstitute an active GALA protein and thereby drive expression of the HIS3 gene. Colonies that express HIS3 can then be purified from these strains and used to produce and isolate the bait oct-3 gene-interacting protein using techniques routinely practiced in the art.

[0127] Detection of OCT-3 Protein or oct-3 Nucleic Acid and Diagnostic Assays

[0128] The invention encompasses methods for detecting the presence of OCT-3 protein or nucleic acid in a biological sample as well as methods for measuring the level of OCT-3 protein or nucleic acid in a biological sample. Such methods are useful for diagnosis of disorders associated with aberrant expression of OCT-3.

[0129] An exemplary method for detecting the presence or absence of OCT-3 in a biological sample involves obtaining a biological sample from a test subject and contacting the biological sample with a compound or an agent capable of detecting an OCT-3 polypeptide or an oct-3 nucleic acid (e.g., mRNA or genomic DNA) that encodes an OCT-3 polypeptide. A preferred agent for detecting oct-3 mRNA or genomic DNA is a labeled nucleic acid probe capable of hybridizing to oct-3 mRNA or genomic DNA. The nucleic acid probe can be, for example, a full-length oct-3 nucleic acid molecule, such as a nucleic acid molecule having the sequence of SEQ ID NO:1, SEQ ID NO:3, or SEQ ID NO:5, or a portion thereof, such as an oligonucleotide of at least 15, 30, 50, 100, 250, or 500 nucleotides in length and sufficient to specifically hybridize under stringent conditions to oct-3 mRNA or genomic DNA.

[0130] A preferred agent for detecting an OCT-3 polypeptide is an antibody capable of binding to an OCT-3 polypeptide, preferably an antibody with a detectable label. Antibodies can be polyclonal, or more preferably, monoclonal. An intact antibody, or a fragment thereof (e.g., Fab or F(ab)2) can be used. The term “labeled,” with regard to the probe or antibody, is intended to encompass direct labeling of the probe or antibody by coupling (i.e., physically linking) a detectable substance to the probe or antibody, as well as indirect labeling of the probe or antibody by reactivity with another reagent that is directly labeled. Examples of indirect labeling include detection of a primary antibody using a fluorescently labeled secondary antibody and end-labeling of a DNA probe with biotin such that it can be detected with fluorescently labeled streptavidin. The term “biological sample” is intended to include tissues, cells, and biological fluids isolated from a subject, as well as tissues, cells and fluids present within a subject. That is, the detection method of the invention can be used to detect oct-3 mRNA, an OCT-3 polypeptide, or oct-3 genomic DNA in a biological sample in vitro as well as in vivo. For example, in vitro techniques for detection of oct-3 mRNA include Northern hybridizations and in situ hybridizations. In vitro techniques for detection of an OCT-3 polypeptide include enzyme linked immunosorbent assays (ELISAs), Western blots, immunoprecipitations and immunofluorescence. In vitro techniques for detection of oct-3 genomic DNA include Southern hybridizations. Furthermore, in vivo techniques for detection of an OCT-3 polypeptide include introducing into a subject a labeled anti-OCT-3 antibody. For example, the antibody can be labeled with a radioactive marker whose presence and location in a subject can be detected by standard imaging techniques.

[0131] In one embodiment, the biological sample contains protein molecules from the test subject. Alternatively, the biological sample can contain mRNA molecules from the test subject or genomic DNA molecules from the subject.

[0132] In another embodiment, the methods further involve obtaining a control biological sample from a control subject, contacting the control sample with a compound or agent capable of detecting an OCT-3 polypeptide, oct-3 mRNA, or oct-3 genomic DNA, such that the presence of an OCT-3 polypeptide, oct-3 mRNA, or oct-3 genomic DNA is detected in the biological sample, and comparing the presence of OCT-3 polypeptide, oct-3 mRNA, or genomic DNA in the control sample with the presence of OCT-3 polypeptides, mRNA or genomic DNA in a test sample.

[0133] The invention also encompasses kits for detecting the presence of oct-3 nucleic acid molecules or OCT-3 polypeptides in a biological sample. For example, the kit can contain a labeled compound or agent capable of detecting an OCT-3 polypeptide or an oct-3 mRNA molecule in a biological sample; means for determining the amount of OCT-3 in the sample; and means for comparing the amount of OCT-3 in the sample with a standard. The compound or agent can be packaged in a suitable container. The kit can further contain instructions for using the kit to detect an OCT-3 polypeptide or oct-3 nucleic acid molecule.

[0134] Prognostic Assays

[0135] The invention also encompasses prognostic assays that can be used to identify subjects having or at risk of developing a disease or disorder associated with aberrant oct-3 expression or OCT-3 activity, e.g., a neurological disorder. Thus, the present invention provides a method for identifying a disease or disorder associated with aberrant oct-3 expression or OCT-3 activity in which a test sample is obtained from a subject and oct-3 nucleic acid molecules or OCT-3 polypeptides are detected, wherein the presence of oct-3 nucleic acid or OCT-3 polypeptides can be diagnostic for a subject having or at risk of developing an OCT-3 mediated disease or disorder based on the level of oct-3 expressed or the allelic form of OCT-3 expressed. As used herein, a “test sample” refers to a biological sample obtained from a subject of interest. For example, a test sample can be a biological fluid (e.g., serum), a cell sample, or tissue.

[0136] Furthermore, the prognostic assays described herein can be used to determine whether a subject can be administered an agent (e.g., an agonist, antagonist, peptidomimetic, polypeptide, nucleic acid, small molecule or other drug candidate) to treat a disease or disorder associated with aberrant oct-3 expression or OCT-3 activity. For example, such methods can be used to determine whether a subject can be effectively treated with an agent that modulates OCT-3 expression and/or activity. Thus, the present invention provides methods for determining whether a subject can be effectively treated with an agent for a disorder associated with aberrant oct-3 expression or OCT-3 activity in which a test sample is obtained and oct-3 nucleic acids or OCT-3 polypeptides are detected (e.g., wherein the presence of a particular level of oct-3 expression or a particular OCT-3 allelic variant is diagnostic for a subject that can be administered an agent to treat a disorder associated with aberrant oct-3 expression or OCT-3 activity).

[0137] The methods of the invention can also be used to detect genetic alterations in an oct-3 gene, thereby determining if a subject with the lesioned gene is at risk for a disorder characterized by aberrant extracellular concentrations of molecules normally transported across the cellular membrane by OCT-3. In preferred embodiments, the methods include detecting, in a sample of cells from the subject, the presence or absence of a genetic alteration characterized by at least one alteration affecting the integrity of the gene encoding an OCT-3 polypeptide or the misexpression of the oct-3 gene. For example, such genetic alterations can be detected by ascertaining the existence of at least one of: (1) a deletion of one or more nucleotides from an oct-3 gene; (2) an addition of one or more nucleotides to an oct-3 gene; (3) a substitution of one or more nucleotides of an oct-3 gene; (4) a chromosomal rearrangement of an oct-3 gene; (5) an alteration in the level of a messenger RNA transcript of an oct-3 gene; (6) aberrant modification of an oct-3 gene, such as of the methylation pattern of the genomic DNA, (7) the presence of a non-wild type splicing pattern of a messenger RNA transcript of an oct-3 gene; and (8) inappropriate post-translational modification of an OCT-3 polypeptide. As described herein, there are a large number of assay techniques known in the art which can be used for detecting alterations in an oct-3 gene. A preferred biological sample is a peripheral blood sample obtained by conventional means from a subject.

[0138] In certain embodiments, detection of the alteration involves the use of a probe/primer in a polymerase chain reaction (PCR; see, e.g., U.S. Pat. Nos. 4,683,195 and 4,683,202), such as anchor PCR or RACE PCR, or alternatively, in a ligation chain reaction (LCR; see, e.g., Landegran et al., Science 241:1077-1080, 1988); and Nakazawa et al. Proc. Natl. Acad. Sci. USA 91:360-364, 1994), the latter of which can be particularly useful for detecting point mutations in the oct-3 gene (see Abavaya et al., Nucl. Acids Res. 23:675-681, 1995). This method can include the steps of collecting a sample of cells from a patient, isolating nucleic acid (e.g., genomic DNA, mRNA, or both) from the cells of the sample, contacting the nucleic acid sample with one or more primers which specifically hybridize to an oct-3 gene under conditions such that hybridization and amplification of the oct-3 nucleic acid (if present) occurs, and detecting the presence or absence of an amplification product, or detecting the size of the amplification product and comparing the length to a control sample. It is anticipated that PCR and/or LCR may be desirable to use as a preliminary amplification step in conjunction with any of the techniques used for detecting mutations described herein.

[0139] Alternative amplification methods include: self sustained sequence replication (Guatelli et al., Proc. Natl. Acad. Sci USA 87:1874, 1990), transcriptional amplification system (Kwoh et al., Proc. Natl. Acad. Sci USA 86:1173, 1989), Q-Beta Replicase (Lizardi et al., Bio/Technology 6:1197, 1988), or any other nucleic acid amplification method, followed by the detection of the amplified molecules using techniques well known to those of ordinary skill in the art. These detection schemes are especially useful for the detection of nucleic acid molecules if such molecules are present in very low number.

[0140] In an alternative embodiment, alterations in an oct-3 gene from a sample cell can be identified by identifying changes in a restriction enzyme cleavage pattern. For example, sample and control DNA is isolated, amplified (optionally), digested with one or more restriction endonucleases, and fragment length sizes are determined by gel electrophoresis and compared. Differences in fragment length sizes between sample and control DNA indicates mutations in the sample DNA. Moreover, the use of sequence specific ribozymes (see, e.g., U.S. Pat. No. 5,498,531) can be used to score for the presence of specific mutations by development or loss of a ribozyme cleavage site.

[0141] In other embodiments, alterations in oct-3 can be identified by hybridizing a sample and control nucleic acids, e.g., DNA or RNA, to high density arrays containing tens to thousands of oligonucleotide probes (Cronin et al., Human Mutation 7:244-255 (1996); Kozal et al., Nature Medicine 2:753-759 (1996)). For example, alterations in oct-3 can be identified in two dimensional arrays containing light-generated DNA probes as described in Cronin et al., supra. Briefly, a first hybridization array of probes can be used to scan through long stretches of DNA in a sample and control to identify base changes between the sequences by making linear arrays of sequential overlapping probes. This step allows the identification of point mutations. This step is followed by a second hybridization array that allows the characterization of specific mutations by using smaller, specialized probe arrays complementary to all variants or mutations detected. Each mutation array is composed of parallel probe sets, one complementary to the wild-type gene and the other complementary to the mutant gene.

[0142] In yet another embodiment, any of a variety of sequencing reactions known in the art can be used to directly sequence the oct-3 gene and detect mutations by comparing the sequence of the sample oct-3 with the corresponding wild-type (control) sequence. Examples of sequencing reactions include those based on techniques developed by Maxim and Gilbert (Proc. Natl. Acad. Sci. USA 74:560, 1977)) or Sanger (Proc. Natl. Acad. Sci. USA 74:5463, 1977). It is also contemplated that any of a variety of automated sequencing procedures can be utilized when performing the diagnostic assays (Bio/Techniques 19:448, 1995) including sequencing by mass spectrometry (see, e.g. PCT International Publication No. WO 94/16101; Cohen et al. Adv. Chromatogr. 36:127, 1996; and Griffin et al. Appl. Biochem. Biotechnol. 38:147, 1993).

[0143] Other methods of detecting mutations in the oct-3 gene include methods in which protection from cleavage agents is used to detect mismatched bases in RNA/RNA or RNA/DNA heteroduplexes (Myers et al. Science 230:1242 (1985)). In general, the art technique of “mismatch cleavage” starts by providing heteroduplexes formed by hybridizing (labeled) RNA or DNA containing the wild-type oct-3 sequence with potentially mutant RNA or DNA obtained from a tissue sample. The double-stranded duplexes are treated with an agent which cleaves single-stranded regions of the duplex such as which will exist due to basepair mismatches between the control and smaple strands. For instance, RNA/DNA duplexes can be treated with RNase and DNA/DNA hybrids treated with SI nuclease to enzymatically digest the mismatched regions. In other embodiments, either DNA/DNA or RNA/DNA duplexes can be treated with hydroxylamine or osmium tetroxide and with piperidine in order to digest mismatched regions. After digestion of the mismatched regions, the resulting material is then separated by size on denaturing polyacrylamide gels to determine the site of mutation. (See, for example, Cotton et al., Proc. Natl. Acad. Sci. USA 85:4397, 1988; Saleeba et al., Methods Enzymol. 217:286, 1992.) In a preferred embodiment, the control DNA or RNA can be labeled for detection.

[0144] In still another embodiment, the mismatch cleavage reaction employs one or more proteins that recognize mismatched base pairs in double-stranded DNA (so called “DNA mismatch repair” enzymes) in defined systems for detecting and mapping point mutations in oct-3 cDNAs obtained from samples of cells. For exmaple, the mutY enzyme of E. coli cleaves A at G/A mismatches (Hsu et al. Carcinogenesis 15:1657, 1994). According to an exemplary embodiment, a probe based on an oct-3 sequence is hybridized to a cDNA or other DNA product from a test cell or cells. The duplex is treated with a DNA mismatch repair enzyme, and the cleavage products, if any, can be detected from electrophoresis protocols or the like. See, for example, U.S. Pat. No. 5,459,039.

[0145] In other embodiments, alterations in electrophoretic mobility can be used to identify mutations in oct-3 genes. For example, single strand conformation polymorphism (SSCP) can be used to detect differences in electrophoretic mobility between mutant and wild type nucleic acids (Orita et al., Proc. Natl. Acad. Sci. USA 86:2766; see also Cotton Mutat Res. 285:125, 1993; and Hayashi Genet. Anal. Tech. Appl. 9:73, 1992). Single-stranded DNA fragments of sample and control oct-3 nucleic acids will be denatured and allowed to renature. The secondary structure of single-stranded nucleic acids varies according to sequence, the resulting alteration in electrophoretic mobility enables the detection of even a single base change. The DNA fragments may be labeled or detected with labeled probes. The sensitivity of the assay may be enhanced by using RNA (rather than DNA), in which the secondary structure is more sensitive to a change in sequence. In a preferred embodiment, the method utilizes heteroduplex analysis to separate double stranded heteroduplex molecules on the basis of changes in electrophoretic mobility (Kee et al. Trends Genet. 7:5, 1991).

[0146] In yet another embodiment, the movement of mutant or wild-type fragments in a polyacrylamide gel containing a gradient of denaturant is assayed using denaturing gradient gel electrophoresis (DGGE; Myers et al. Nature 313:495, 1985). When DGGE is used as the method of analysis, DNA will be modified to insure that it does not completely denture, for exmaple by adding a GC clamp of approximtely 40 bp of high-melting GC-rich DNA by PCR. In a further embodiment, a temperature gradient is used in place of a denaturing gradient to identify differences in the mobility of control and sample DNA (Rosenbaum et al. Biophys. Chem. 265:12753, 1987).

[0147] Examples of other techniques for detecting point mutations include, but are not limited to, selective oligonucleotide hybridization, selective amplification, or selective primer extension. For example, oligonucleotide primers may be prepared in which the known mutation is placed centrally and then hybridized to target DNA under conditions which permit hybridization only if a perfect match is found (Saiki et al. Nature 324;163 (1986); Saiki et al., Proc. NAtl. Acad. Sci. USA 86:6230 (1989)). Such allele specific oligonucleotides are hybridized to PCR amplified target DNA or a number of different mutations when the oligonucleotides are attached to the hybridizing membrane and hybridized with labeled target DNA.

[0148] Alternatively, allele specific amplification technology which depends on selective PCR amplification may be used in conjunction with the instant invention. Oligonucleotides used as primers for specific amplification may carry the mutation of interest in the center of the molecule, so that amplification depends on differential hybridization (Gibbs et al., Nucl. Acids Res. 17:2437-2448 (1989)) or at the extreme 3′ end of one primer where, under appropriate conditions, mismatch can prevent, or reduce polymerase extension (Prossner, Tib/Tech 11:238 (1993)). In addition it may be desirable to introduce a novel restriction site in the region of the mutation to create cleavage-based detection (Gasparini et al., Mol. Cell Probes 6:1 (1992)). It is anticipated that in certain embodiments amplification may also be performed using Taq ligase for amplification (Barany, Proc. Natl. Acad. Sci. USA 88:89 (1991)). In such cases, ligation will occur only if there is a perfect match at the 3′ end of the 5′ sequence making it possible to detect the presence of a known mutation at a specific site by looking for the presence of absence of amplification.

[0149] The methods described herein may be performed, for example, by utilizing pre-packaged diagnostic kits comprising at least one probe nucleic acid or antibody reagent described herein, which may be conveniently used, for example, in a clinical setting to diagnose patient exhibiting symptoms or a family history of a disease or disorder involving abnormal OCT-3 activity.

[0150] Pharmacogenetics

[0151] Agents or modulators which have a stimulatory or inhibitory effect on OCT-3 activity (including those that alter activity by altering oct-3 gene expression), identified by a screening assay described herein, can be administered to individuals to treat, prophylactically or therapeutically, disorders (e.g., neurological disorders, pain disorders) associated with aberrant OCT-3 activity.

[0152] A therapeutic agent includes, but is not limited to, small molecules, peptides, antibodies, ribozymes and antisense oligonucleotides. With regard to both prophylactic and therapeutic methods of treatment, such treatments can be specifically tailored or modified, based on knowledge obtained from the field of pharmacogenetics (i.e., the study of the relationship between an individual's genotype and that individual's response to a foreign compound or drug). Thus, the pharmacogenetics of the individual permits the selection of effective agents (e.g., drugs) for prophylactic or therapeutic treatments based on a consideration of the individual's genotype. Such pharmacogenetics can further be used to determine appropriate dosages and therapeutic regimens. Accordingly, the activity of OCT-3 polypeptides, expression of oct-3 nucleic acids, or mutation content of oct-3 genes in an individual can be determined to thereby select appropriate agents for therapeutic or prophylactic treatment of the individual.

[0153] As used herein, the term “treatment” is defined as the application or administration of a therapeutic agent to a patient, or application or administration of a therapeutic agent to an isolated tissue or cell line from a patient, who has a disease, a symptom of disease or a predisposition toward a disease, with the purpose to cure, heal, alleviate, relieve, alter, remedy, ameliorate, improve or affect the disease, the symptoms of disease or the predisposition toward disease.

[0154] Pharmacogenetics deals with clinically significant hereditary variations in the response to drugs due to altered drug disposition and abnormal action in affected persons. (See, e.g., Eichelbaum, Clin. Exp. Pharmacol. Physiol. 23:983, 1996 and Linder, Clin. Chem. 43:254, 1997.) In general, two types of pharmacogenetic conditions can be differentiated. Genetic conditions transmitted as a single factor altering the way drugs act on the body (altered drug action) or genetic conditions transmitted as single factors altering the way the body acts on drugs (altered drug metabolism). These pharmacogenetic conditions can occur either as rare defects or as polymorphisms. For example, glucose-6-phosphate dehydrogenase deficiency (G6PD) is a common inherited enzymopathy in which the main clinicl complication is haemolysis after ingestion of oxidant drugs (anti-malarials, sulfonamides, analgesics, nitrofurans) and consumption of fava beans.

[0155] As an illustrative embodiment, the activity of drug metabolizing enzymes is a major determinant of both the intensity and duration of drug action. The discovery of genetic polymorphisms of drug metabolizing enzymes (e.g. N-acetyltransferase (NAT2) and cytochrome P450 enzymes CYP2D6 and CYP2C19) has provided an explanation as to why some patients do not obtain the expected drug effects or show exaggerated drug response and serious toxicity after taking the standard and safe dose of a drug. These polymorphisms are expressed in two phenotypes in the population, the extensize metabolizer (EM) and poor metabolizer (PM). The prevalence of PM is different among different populations. For example, the gene coding for CYP2D6 is highly polymorphic and several mutations have been identified in PM, which all lead to the absence of functional CYP2D6. Poor metabolizers of CYP2D6 and CYP2C19 quite frequently experience exaggerated drug response and side effects when they receive standard doses. If a metabolite is the active therapeutic moiety, PM show no therapeutic response, as demonstrated for the analgesic effect of codeine mediated by its CYP2D6-formed metabolite morphine.

[0156] The other extreme is the so called ultra-rapid metabolizers who do not respond to standard doses. Recently, the molecular basis of ultra-rapid metabolism has been identified to be due to CYP2D6 gene amplification.

[0157] Thus, the activity of OCT-3 polypeptide, expression of oct-3 nucleic acid, or mutation content of oct-3 gene in an individual can be determined to thereby select appropriate agents for therapeutic or prophylactic treatment of the individual. In addition, pharmacogenetic studies can be used to apply genotyping of polymorphic alleles encoding drug-metabolizing enzymes to the identification of an individual's drug responsiveness phenotype. This knowledge, when applied to dosing or drug selection, can avoid adverse reactions or therapeutic failure and thus enhance therapeutic or prophylactic efficiency when treating a subject with an OCT-3 modulator, such as a modulator identified by one of the exemplary screening assays described herein.

[0158] Monitoring of Effects During Clinical Trials

[0159] Monitoring the influence of agents (e.g., drugs, compounds) on the expression of oct-3 or the activity OCT-3 (e.g., the ability to modulate the symptoms associated with neurological disorders) can be applied not only in basic drug screening, but also in clinical trials. For example, the effectiveness of an agent determined by a screening assay as described herein to increase oct-3 gene expression, OCT-3 polypeptide levels, or upregulate OCT-3 activity, can be monitored in clinical trials of subjects exhibiting decreased oct-3 gene expression, decreased OCT-3 polypeptide levels, or downregulated OCT-3 activity. Alternatively, the effectiveness of an agent determined by a screening assay to decrease oct-3 gene expression, decrease OCT-3 polypeptide levels, or downregulate OCT-3 activity, can be monitored in clinical trials of subjects exhibiting increased oct-3 gene expression, increased OCT-3 polypeptide levels, or upregulated OCT-3 activity. In such clinical trials, the expression of oct-3 or activity of OCT-3 can be used as a “read out” or marker of the responsiveness of a particular cell.

[0160] For example, and not by way of limitation, genes, including oct-3, that are modulated in cells by treatment with an agent (e.g., a compound, drug, or small molecule) that modulates OCT-3 activity (e.g., identified in a screening assay as described herein) can be identified. Thus, to study the effect of agents on neurolgoical disorders, for example, in a clinical trial, cells can be isolated and RNA prepared and analyzed for the level of oct-3 expression and other genes implicated in the neurological disorder. The levels of gene expression (i.e., a gene expression pattern) can be quantified by Northern blot analysis or RT-PCR, as described herein, or alternatively by measuring the amount of polypeptide produced, by one of the methods described herein, or by measuring the levels of activity of OCT-3 or other genes. In this way, the gene expression pattern can serve as an indicative marker of the physiological response of the cells to the agent. Accordingly, this response state can be determined before, and at various points during, treatment of the individual with the agent.

[0161] In a preferred embodiment, the present invention provides a method for monitoring the effectiveness of treatment of a subject with an agent (e.g., an agonist, antagonist, peptidomimetic, polypeptide, nucleic acid, small molecule, or other drug candidate identified by the ascreening assays described herein) comprising the steps of (1) obtaining a pre-administration sample from a subject prior to administration of the agent; (2) detecting the level of expression of an OCT-3 polypeptide or oct-3 mRNA in the pre-administration sample, or the level or activity of oct-3; (3) obtaining one or more post-administration samples from the subject; (4) detecting the level of expression of oct-3 mRNA or the level or activity of the OCT-3 polypeptide in the post-administration sample; (5) comparing the level of expression of oct-3 mRNA in the pre-administration sample with that in the post-administration sample, or comparing the level or activity of the OCT-3 polypeptide in the pre-administration sample with that in the post-administration sample; and (6) altering the administration of the agent to the subject accordingly.

[0162] Screening Assays

[0163] The invention also provides methods (also referred to herein as “screening assays”) for identifying modulators, i.e., candidate or test compounds or agents (e.g., including peptides, proteins and antibodies, and fragments thereof, peptidomimetics, small molecules, ribozymes, and oct-3 antisense molecules) which bind to OCT-3 proteins, have a stimulatory or inhibitory effect on oct-3 expression or OCT-3 activity, or have a stimulatory or inhibitory effect on the expression or activity of an OCT-3 target molecule. Compounds identified using the assays described herein are useful for treating pain and neurological disorders.

[0164] Candidate or test compounds or agents which interact with (e.g., bind) OCT-3 and/or have a stimulatory or inhibitory effect on the activity or the expression of OCT-3 are identified in assays that employ either cell-based assays using cells which express a form of oct-3 or cell-free assays using a form of isolated OCT-3. The various assays can employ any of a variety of forms of OCT-3 (e.g., full-length OCT-3, a biologically active fragment of OCT-3, or a fusion protein which includes all or a portion of OCT-3). Moreover, the OCT-3 can be derived from any suitable mammalian species (e.g., human, rat, mouse, monkey), e.g., including, but not limited to, human OCT-3, rat OCT-3, and murine OCT-3. The assay can be a binding assay using direct or indirect measurement of the binding of a test compound or an OCT-3 ligand to OCT-3 itself. Alternatively, the assay can be an assay using direct or indirect measurement of a biological activity of OCT-3. The assay can also be an expression assay using direct or indirect measurement of the expression of OCT-3 (e.g., mRNA encoding an OCT-3 protein, or fragment thereof). Additionally, the various screening assays can be combined with an in vivo assay of the effect of the test compound on a suitable mammal (e.g., including, but not limited to, a mouse or a rat) model of a neurological or pain disorder

[0165] In one aspect, the assay is a cell-based assay in which a cell expressing a membrane-bound form of an OCT-3 protein, e.g., a full length OCT-3, a biologically active fragment of OCT-3, or a fusion protein which includes all or a fragment of OCT-3, (e.g., a neuronal cell or a cell transfected with a nucleic acid molecule encoding an OCT-3 protein, e.g., SEQ ID NOs:2, 4, or 6, or a fragment thereof) is contacted with a test compound, and the ability of the test compound to modulate OCT-3 activity is determined. In a preferred embodiment, the biologically active fragment of the OCT-3 protein includes a domain or motif which can modulate an OCT-3 activity, e.g., transport of an ion or an organic molecule. Alternatively, determining the ability of the test compound to modulate OCT-3 activity can be accomplished by monitoring, for example, the production of one or more specific metabolites (e.g., 14C-glucose) or replacement of nutrients in a cell which expresses an OCT-3 protein (see, e.g., Saada et al. (2000) Biochem. Biophys. Res. Commun. 269:382-386).

[0166] In another aspect, determining the ability of the test compound to modulate the activity of OCT-3 can be achieved, for example, by determining the ability of OCT-3 to bind to or interact with a target molecule. The target molecule can be a molecule with which OCT-3 binds or interacts with in nature, for example, a molecule on the surface of a cell which co-expresses OCT-3, a molecule on the surface of a second cell, a molecule in the extracellular milieu, a molecule associated with the internal surface of a cell membrane, or a cytoplasmic molecule. The target molecule can be a component of a signal transduction pathway which facilitates transduction of an extracellular signal (e.g., a signal generated by binding of an OCT-3 ligand to OCT-3) through the cell membrane and into the cell. The target molecule can be, for example, a second intracellular protein which has catalytic activity or a protein which facilitates the association of downstream signaling molecules with OCT-3.

[0167] Determining the ability of an OCT-3 polypeptide to bind to or interact with a target molecule can be accomplished by any of the methods described herein for determining direct binding. In one embodiment, determining the ability of a polypeptide of the invention to bind to or interact with a target molecule can be accomplished by determining the activity of the target molecule. For example, the activity of the target molecule can be determined by detecting induction of a cellular second messenger of the target (e.g., intracellular Ca2+, IP3, etc.), detecting catalytic/enzymatic activity of the target on an appropriate substrate, detecting the induction of a reporter gene (e.g., a regulatory element that is responsive to a polypeptide of the invention operably linked to a nucleic acid encoding a detectable marker, e.g., luciferase), or detecting a cellular response.

[0168] A competitive binding format is useful to identify compounds that interfere with the interaction between OCT-3 and a binding partner. The assay involves contacting an OCT-3-expressing cell (e.g., a neuronal cell or a cell transfected with a nucleic acid molecule encoding an OCT-3 protein, e.g., SEQ ID NOs: 1, 3, or 5, or a fragment thereof) or an OCT-3 polypeptide (e.g., SEQ ID NOs:2, 4, or 6, or a peptide or fusion protein thereof) with a compound known to bind OCT-3 under conditions and for a time sufficient to allow formation of a complex. In order to test a compound for inhibitory activity, the reaction mixture is prepared in the presence and absence of the test compound. The test compound may be initially included in the reaction mixture, or may be added at a time subsequent to the addition of OCT-3 and its binding partner. Control reaction mixtures are incubated without the test compound or with a non-active control compound. The formation of any complexes between the OCT-3 moiety and the binding partner is then detected. The formation of a complex in the control reaction, but not in the reaction mixture containing the test compound, indicates that the compound interferes with the interaction of the OCT-3 and the interactive binding partner. Additionally, complex formation within reaction mixtures containing the test compound and normal OCT-3 protein may also be compared to complex formation within reaction mixtures containing the test compound and a mutant OCT-3. This comparison may be important in those cases wherein it is desirable to identify compounds that disrupt interactions of mutant but not normal OCT-3.

[0169] The assay for compounds that interfere with the interaction of the OCT-3 and binding partners can be conducted in a heterogeneous or homogeneous format. Heterogeneous assays involve anchoring either the OCT-3 protein, polypeptide, peptide, or fusion protein, or the binding partner onto a solid phase and detecting complexes anchored on the solid phase at the end of the reaction. In homogeneous assays, the entire reaction is carried out in a liquid phase. In either approach, the order of addition of reactants can be varied to obtain different information about the compounds being tested. For example, test compounds that interfere with the interaction by competition can be identified by conducting the reaction in the presence of the test substance; i.e., by adding the test substance to the reaction mixture prior to or simultaneously with OCT-3 and its binding partner. Alternatively, test compounds that disrupt preformed complexes, e.g., compounds with higher binding constants that displace one of the components from the complex, can be tested by adding the test compound to the reaction mixture after complexes have been formed.

[0170] To determine whether a test compound modulates oct-3 expression, a cell which expresses OCT-3 (e.g., a brain cell or a cell transfected with a nucleic acid molecule encoding an OCT-3 protein, e.g., SEQ ID NO: 1, 3, or 5, or a fragment thereof) is contacted with a test compound, and the ability of the test compound to modulate oct-3 expression is determined by measuring oct-3 mRNA by, e.g., Northern Blotting, quantitative PCR (e.g., TaqMan®), or in vitro transcriptional assays. To perform an in vitro transcriptional assay, the full length promoter and enhancer of OCT-3 can be linked to a reporter gene, such as chloramphenicol acetyltransferase (CAT) or luciferase, and introduced into host cells. The same host cells are then transfected with or contacted with the test compound. The effect of the test compound can be measured by reporter gene activity and then compared to reporter gene activity in cells which do not contain the test compound. A difference, e.g., an increase or decrease, in reporter gene activity relative to activity in cells which do not contain the test compound therefore indicates a modulation of oct-3 expression by the test compound.

[0171] Alternatively, modulators of oct-3 expression can be identified using a method in which a cell is contacted with a candidate compound and the expression of OCT-3 protein or oct-3 mRNA in the cell is determined. The level of expression of OCT-3 protein or mRNA in the presence of the candidate compound is compared to the level of expression of OCT-3 protein or oct-3 mRNA in the absence of the candidate compound. The candidate compound is then identified as a modulator of expression of oct-3 based on this comparison. For example, when expression of OCT-3 protein or mRNA protein is greater (i.e., statistically significantly greater) in the presence of the candidate compound than in its absence, the candidate compound is identified as a stimulator or agonist of OCT-3 protein synthesis or mRNA expression. Alternatively, when expression of OCT-3 protein or mRNA is less (i.e., statistically significantly less) in the presence of the candidate compound than in its absence, the candidate compound is identified as an inhibitor or antagonist of OCT-3 protein synthesis or mRNA expression. The level of OCT-3 protein or mRNA in the cells can be determined by any of the methods described herein.

[0172] In another embodiment, an assay is a cell-based assay comprising contacting a cell expressing an OCT-3 target molecule (e.g., an OCT-3 substrate) with a test compound and determining the ability of the test compound to modulate (e.g., stimulate or inhibit) the activity of the OCT-3 target molecule. Determining the ability of the test compound to modulate the activity of an OCT-3 target molecule can be accomplished, for example, by determining the ability of the OCT-3 polypeptide to bind to or interact with the OCT-3 target molecule.

[0173] Determining the ability of the OCT-3 polypeptide, or a biologically active fragment thereof, to bind to or interact with an OCT-3 target molecule can be accomplished by one of the methods described above for determining direct binding. In a preferred embodiment, determining the ability of the OCT-3 polypeptide to bind to or interact with an OCT-3 target molecule can be accomplished by determining the activity of the target molecule. For example, the activity of the target molecule can be determined by detecting induction of a cellular second messenger of the target (i.e., intra-cellular Ca2+, diacylglycerol, IP3, and the like), detecting catalytic/enzymatic activity of the target using an appropriate substrate, detecting the induction of a reporter gene (comprising a target-responsive regulatory element operatively linked to a nucleic acid encoding a detectable marker, e.g., luciferase), or detecting a target-regulated cellular response.

[0174] In another embodiment, an assay of the invention is a cell-free assay in which an OCT-3 protein, or biologically active portion thereof, is contacted with a test compound, and the ability of the test compound to bind or modulate (e.g., stimulate or inhibit) the activity of the OCT-3 protein, or biologically active portion thereof, is determined. Preferred biologically active portions of the OCT-3 proteins to be used in assays of the invention include fragments which participate in interactions with non-OCT-3 molecules, e.g., fragments with high surface probability scores.

[0175] Binding of the test compound to the OCT-3 protein can be determined either directly or indirectly as described herein. Determining the ability of the OCT-3 protein to bind to a test compound can also be accomplished using a technology such as real-time Biomolecular Interaction Analysis (BIA) (Sjolander, S. and Urbaniczky, C. (1991) Anal. Chem. 63:2338-2345; Szabo et al. (1995) Curr. Opin. Struct. Biol. 5:699-705). As used herein, “BIA” is a technology for studying biospecific interactions in real time, without labeling any of the interactants (e.g., BIAcore). Changes in the optical phenomenon of surface plasmon resonance (SPR) can be used as an indication of real-time reactions between biological molecules.

[0176] In an alternative embodiment, determining the ability of the test compound to modulate the activity of an OCT-3 polypeptide can be accomplished by determining the ability of the OCT-3 polypeptide to further modulate the activity of a downstream effector of an OCT-3 target molecule. For example, the activity of the effector molecule on an appropriate target can be determined or the binding of the effector to an appropriate target can be determined as previously described.

[0177] In another aspect, the assay is a cell-free assay in which the ability of a test compound to modulate OCT-3 interaction (e.g., binding) with an OCT-3 target molecule (e.g., an OCT-3 substrate or ligand) is determined. Determining the ability of a test compound to modulate OCT-3 binding to a substrate can be accomplished, for example, by coupling the OCT-3 substrate with a radioisotope or fluorescent or enzymatic label such that binding of the OCT-3 substrate to OCT-3 can be determined by detecting the presence of the labeled OCT-3 substrate in a complex. Alternatively, OCT-3 can be coupled with a radioisotope or enzymatic label to monitor the ability of a test compound to modulate OCT-3 binding to an OCT-3 substrate in a complex. Determining the ability of the test compound to bind OCT-3 can be accomplished, for example, by coupling the compound with a radioisotope or enzymatic label such that binding of the compound to OCT-3 can be determined by detecting the labeled OCT-3 compound in a complex. For example, OCT-3 substrates can be labeled with 125I, 35S, 14C, or 3H, either directly or indirectly, and the radioisotope detected by direct counting of radioemission or by scintillation counting. Alternatively, compounds can be enzymatically labeled with, for example, horseradish peroxidase, alkaline phosphatase, or luciferase, and the enzymatic label detected by determination of conversion of an appropriate substrate to product.

[0178] It is also within the scope of this invention to determine the ability of a compound to interact with (e.g., bind) OCT-3 without the labeling of any of the interactants. For example, a microphysiometer can be used to detect the interaction of a compound with OCT-3 without the labeling of either the compound or the OCT-3 (McConnell, H. M. et al. (1992) Science 257:1906-1912). As used herein, a “microphysiometer” (e.g., Cytosensor®; Molecular Devices Corp., Sunnyvale Calif.) is an analytical instrument that measures the rate at which a cell acidifies its environment using a light-addressable potentiometric sensor (LAPS). Changes in this acidification rate can be used as an indicator of the interaction between a compound and OCT-3.

[0179] In yet another embodiment, the cell-free assay involves contacting an OCT-3 protein, or biologically active portion thereof, with a known compound which binds the OCT-3 protein to form an assay mixture, contacting the assay mixture with a test compound, and determining the ability of the test compound to interact with the OCT-3 protein, wherein determining the ability of the test compound to interact with the OCT-3 protein comprises determining the ability of the OCT-3 protein to preferentially bind to or modulate the activity of an OCT-3 target molecule (e.g., an OCT-3 substrate or ligand). The cell-free assays of the invention are amenable to use of both soluble and/or membrane-bound forms of isolated proteins (e.g., OCT-3 proteins or biologically active portions thereof). In the case of cell-free assays in which a membrane-bound form of an isolated protein is used, it may be desirable to utilize a solubilizing agent such that the membrane-bound form of the isolated protein is maintained in solution. Examples of such solubilizing agents include non-ionic detergents such as n-octylglucoside, n-dodecylglucoside, n-dodecylmaltoside, octanoyl-N-methylglucamide, decanoyl-N-methylglucamide, Triton® X-100, Triton® X-114, Thesit®, Isotridecypoly(ethylene glycol ether)n, 3-[(3-cholamidopropyl)dimethylamminio]-1-propane sulfonate (CHAPS), 3-[(3-cholamidopropyl)dimethylamminio]-2-hydroxy-1-propane sulfonate (CHAPSO), or N-dodecyl=N,N-dimethyl-3-ammonio-1-propane sulfonate.

[0180] In more than one embodiment of the above assay methods of the invention, it may be desirable to immobilize either OCT-3 or an OCT-3 target molecule to facilitate separation of complexed from uncomplexed forms of one or both of the proteins, as well as to accommodate automation of the assay. Binding of a test compound to an OCT-3 protein, or interaction of an OCT-3 protein with an OCT-3 target molecule in the presence and absence of a test compound, can be accomplished in any vessel suitable for containing the reactants. Examples of such vessels include microtitre plates, test tubes, and micro-centrifuge tubes. In one embodiment, a fusion protein can be provided which adds a domain that allows one or both of the proteins to be bound to a matrix. For example, glutathione-S-transferase (GST)/OCT-3 fusion proteins or GST/target fusion proteins can be adsorbed onto glutathione sepharose beads (Sigma Chemical, St. Louis, Mo.) or glutathione derivatized microtitre plates, which are then combined with the test compound or the test compound and either the non-adsorbed target protein or OCT-3 protein, and the mixture incubated under conditions conducive to complex formation (e.g., at physiological conditions for salt and pH). Following incubation, the beads or microtitre plates are washed to remove any unbound components, the matrix is immobilized in the case of beads, and complex formation is determined either directly or indirectly, for example, as described above. Alternatively, the complexes can be dissociated from the matrix under appropriate conditions to permit measurement of OCT-3 binding or activity using standard techniques.

[0181] Other techniques for immobilizing proteins or cell membrane preparations on matrices can also be used in the screening assays of the invention. For example, either an OCT-3 protein or an OCT-3 target molecule can be immobilized utilizing conjugation of biotin and streptavidin. Biotinylated OCT-3 protein or target molecules can be prepared from biotin-NHS (N-hydroxy-succinimide) using techniques known in the art (e.g., biotinylation kit, Pierce Chemicals, Rockford, Ill.), and immobilized in the wells of streptavidin-coated 96 well plates (Pierce Chemicals). Alternatively, antibodies which are reactive with OCT-3 protein or target molecules but which do not interfere with binding of the OCT-3 protein to its target molecule can be derivatized to the wells of the plate, and unbound target or OCT-3 protein will be trapped in the wells by antibody conjugation. Methods for detecting such complexes, in addition to those described above for the GST-immobilized complexes, include immunodetection of complexes using antibodies reactive with the OCT-3 protein or target molecule, as well as enzyme-linked assays which rely on detecting an enzymatic activity associated with the OCT-3 protein or target molecule.

[0182] In another embodiment, modulators of oct-3 expression are identified in a method wherein a cell is contacted with a candidate compound and the expression of oct-3 mRNA or polypeptide in the cell is determined. The level of expression of oct-3 mRNA or OCT-3 polypeptide in the presence of the candidate compound is compared to the level of expression of oct-3 mRNA or polypeptide in the absence of the candidate compound. The candidate compound can then be identified as a modulator of oct-3 expression based on this comparison. For example, when expression of oct-3 mRNA or polypeptide is greater (statistically significantly greater) in the presence of the candidate compound than in its absence, the candidate compound is identified as a stimulator of oct-3 mRNA or polypeptide expression. Alternatively, when expression of oct-3 mRNA or polypeptide is less (statistically significantly less) in the presence of the candidate compound than in its absence, the candidate compound is identified as an inhibitor of oct-3 mRNA or polypeptide expression. The level of oct-3 mRNA or polypeptide expression in the cells can be determined by methods described herein for detecting oct-3 mRNA or polypeptide.

[0183] In another embodiment, the OCT-3 protein, or fragments thereof, can be used as “bait proteins” in a two-hybrid assay or three-hybrid assay (see, e.g., U.S. Pat. No. 5,283,317; Zervos et al. (1993) Cell 72:223-232; Madura et al. (1993) J. Biol. Chem. 268:12046-12054; Bartel et al. (1993) Biotechniques 14:920-924; Iwabuchi et al. (1993) Oncogene 8:1693-1696; and PCT Publication No. WO 94/10300) to identify other proteins which bind to or interact with OCT-3 (“OCT-3 binding proteins” or “OCT-3 bp”) and are involved in OCT-3 activity. Such OCT-3 binding proteins are also likely to be involved in the propagation of signals by the OCT-3 proteins or OCT-3 target molecules as, for example, downstream elements of an OCT-3 mediated signaling transduction pathway. Alternatively, such OCT-3 binding proteins are inhibitors or antagonists of OCT-3 activity.

[0184] In another aspect, the invention is a combination of two or more of the assays described herein. For example, a modulating agent can be identified using a cell-based or a cell-free assay, and the ability of the agent to modulate the activity of an OCT-3 protein can be confirmed in vivo, e.g., in an animal such as an animal model for a neurological disorder, e.g., a pain disorder. Examples of animals that can be used include an oct-3 transgenic mouse, e.g., as described above. Other examples of animals that are useful include non-recombinant, non-genetic animal models of pain such as, for example, surgically treated rats in which the sciatic nerve has been constricted or transected, or rats treated with a plantar injection of complete Freunds' adjuvant to induce inflammatory pain.

[0185] In addition to animal models for neurological disease, e.g., a pain disorder, transgenic animals that express a human OCT-3 can be used to confirm the in vivo effects of a modulator of OCT-3 identified by a cell-based or cell-free screening assay described herein. Animals of any non-human species, including, but not limited to, mice, rats, rabbits, guinea pigs, pigs, micro-pigs, goats, and non-human primates, e.g., baboons, monkeys, and chimpanzees, may be used to generate OCT-3 transgenic animals. Alternatively, the transgenic animal comprises a cell, or cells, that includes a gene which misexpresses an endogenous OCT-3 orthologue such that expression is disrupted, e.g., a knockout animal. Such animals are also useful as a model for studying the disorders which are related to mutated or misexpressed OCT-3 alleles.

[0186] As previously described, any technique known in the art can be used to introduce the human OCT-3 transgene into non-human animals to produce the founder lines of transgenic animals.

[0187] Moreover, an OCT-3 modulator identified as described herein (e.g., an antisense OCT-3 nucleic acid molecule, an OCT-3-specific antibody, or a small molecule) can be used in an animal model to determine the efficacy, toxicity, or side effects of treatment with such a modulator. Alternatively, an OCT-3 modulator identified as described herein can be used in an animal model to determine the mechanism of action of such a modulator.

[0188] Test Compounds

[0189] Candidate/test compounds include, for example, 1) peptides such as soluble peptides, including Ig-tailed fusion peptides and members of random peptide libraries (see, e.g., Lam, K. S. et al. (1991) Nature 354:82-84; Houghten, R. et al. (1991) Nature 354:84-86) and combinatorial chemistry-derived molecular libraries made of D- and/or L-configuration amino acids; 2) phosphopeptides (e.g., members of random and partially degenerate, directed phosphopeptide libraries, see, e.g., Songyang, Z. et al. (1993) Cell 72:767-778); 3) antibodies (e.g., polyclonal, monoclonal, humanized, anti-idiotypic, chimeric, and single chain antibodies as well as Fab, F(ab)2, Fab expression library fragments, and epitope-binding fragments of antibodies); and 4) small organic and inorganic molecules (e.g., molecules obtained from combinatorial and natural product libraries).

[0190] As used herein, small molecules include, but are not limited to, peptidomimetics, amino acids, amino acid analogs, polynucleotides, polynucleotide analogs, nucleotides, nucleotide analogs, organic or inorganic compounds (i.e., including heteroorganic and organometallic compounds) having a molecular weight less than about 10,000 grams per mole, organic or inorganic compounds having a molecular weight less than about 5,000 grams per mole, organic or inorganic compounds having a molecular weight less than about 1,000 grams per mole, organic or inorganic compounds having a molecular weight less than about 500 grams per mole, and salts, esters, and other pharmaceutically acceptable forms of such compounds.

[0191] The test compounds of the invention can be obtained using any of the numerous approaches in combinatorial library methods known in the art, including: biological libraries; spatially addressable parallel solid phase or solution phase libraries; synthetic library methods requiring deconvolution; the ‘one-bead one-compound’ library method; and synthetic library methods using affinity chromatography selection. The biological library approach is limited to peptide libraries, while the other four approaches are applicable to peptide, non-peptide oligomer or small molecule libraries of compounds (Lam, K. S. (1997) Anticancer Drug Des. 12:145).

[0192] Examples of methods for the synthesis of molecular libraries can be found in the art, for example in: DeWitt et al. (1993) Proc. Natl. Acad. Sci. USA 90:6909; Erb et al. (1994) Proc. Natl. Acad. Sci. USA 91:11422; Zuckermann et al. (1994) J. Med. Chem. 37:2678; Cho et al. (1993) Science 261:1303; Carrell et al. (1994) Angew. Chem. Int. Ed. Engl. 33:2059; Carell et al. (1994) Angew. Chem. Int. Ed. Engl. 33:2061; and Gallop et al. (1994) J. Med. Chem. 37:1233.

[0193] Libraries of compounds may be presented in solution (e.g., Houghten (1992) Biotechniques 13:412-421), or on beads (Lam (1991) Nature 354:82-84), chips (Fodor (1993) Nature 364:555-556), bacteria (Ladner, U.S. Pat. No. 5,223,409), spores (Ladner, supra), plasmids (Cull et al. (1992) Proc. Natl. Acad. Sci. USA 89:1865-1869) or phage (Scott and Smith (1990) Science 249:386-390; Devlin (1990) Science 249:404-406; Cwirla et al. (1990) Proc. Natl. Acad. Sci. USA 87:6378-6382; Felici (1991) J. Mol. Biol. 222:301-310; Ladner supra.).

[0194] Modeling of Modulators

[0195] Computer modeling and searching technologies permit identification of compounds, or an improvement of already identified compounds, that can modulate OCT-3 expression or activity. Having identified such a compound or composition enables identification of active sites or regions. Such active sites are often ligand binding sites. The active site can be identified using methods known in the art including, for example, from the amino acid sequences of peptides, from the nucleotide sequences of nucleic acids, or from studies of complexes of the relevant compound or composition with its natural ligand. In the latter case, chemical or X-ray crystallographic methods are useful in identifying residues in the active site by locating the position of the complexed ligand.

[0196] The three dimensional geometric structure of the active site can be determined using known methods, including X-ray crystallography, from which spatial details of the molecular structure can be obtained. Additionally, solid or liquid phase NMR can be used to determine certain intramolecular distances. Any other experimental method of structure determination known in the art can be used to obtain partial or complete geometric structures. The geometric structures measured with a complexed ligand, natural or artificial, can increase the accuracy of the active site structure determined.

[0197] If only an incomplete or insufficiently accurate structure is determined, methods of computer based numerical modeling can be used to complete or improve the accuracy of the structure. Any recognized modeling method may be used, including parameterized models specific to particular biopolymers, such as proteins or nucleic acids, molecular dynamics models based on computing molecular motions, statistical mechanics models based on thermal ensembles, or combined models. For most types of models, standard molecular force fields, which include the forces between constituent atoms and groups, are necessary, and can be selected from force fields known in physical chemistry. The incomplete or less accurate experimental structures can serve as constraints on the complete and more accurate structures computed by these modeling methods.

[0198] Having determined the structure of the active site, either experimentally, by modeling, or by a combination of approaches, candidate modulating compounds can be identified by searching databases containing compounds along with information on their molecular structure. Such searches seek compounds having structures that match the determined active site structure and that interact with the groups defining the active site. Such a search can be manual, but is preferably computer assisted. Compounds identified using these search methods can be tested in any of the screening assays described herein to verify their ability to modulate OCT-3 activity.

[0199] Alternatively, these methods can be used to identify improved modulating compounds from an already known modulating compound or ligand. The composition of the known compound can be modified and the structural effects of the modification can be determined by applying the experimental and computer modeling methods described above to the new composition. The altered structure is then compared to the active site structure of the compound to determine if an improved fit or interaction results. In this manner systematic variations in composition, such as by varying side groups, can be quickly evaluated to obtain modified modulating compounds or ligands of improved specificity or activity.

[0200] Kaul (1998) Prog. Drug Res. 50:9-105 provides a review of modeling techniques for the design of receptor ligands and drugs. Computer programs that screen and graphically depict chemicals are available from companies such as BioDesign, Inc. (Pasadena, Calif.), Oxford Molecular Design (Oxford, UK), and Hypercube, Inc. (Cambridge, Ontario).

[0201] Although described above with reference to design and generation of compounds which can alter binding, one can also screen libraries of known compounds, including natural products or synthetic chemicals, and biologically active materials, including proteins, for compounds which are inhibitors (e.g., antagonists) or stimulators (e.g., agonists).

[0202] Methods for Reducing oct-3 Expression

[0203] Oct-3 gene expression can be reduced through the use of modulatory compounds identified through the use of the screening methods described above. In addition, endogenous oct-3 gene expression can also be reduced by inactivating or “knocking out” the oct-3 gene or its promoter using targeted homologous recombination (see, for example, U.S. Pat. No. 5,464,764). For example, a mutant, non-functional oct-3 (or a completely unrelated DNA sequence) flanked by DNA homologous to the endogenous oct-3 gene (either the coding regions or regulatory regions of the oct-3 gene) can be used, with or without a selectable marker and/or a negative selectable marker, to transfect cells that express oct-3 in vivo. Insertion of the DNA construct, via targeted homologous recombination, results in inactivation of the oct-3 gene. Such approaches are particularly suited for use in developing animal models to study the role of OCT-3; in this instance, modifications to ES (embryonic stem) cells can be used to generate animal offspring with an inactive oct-3 gene. However, a knock out approach can be adapted for use in humans, provided the recombinant DNA constructs are directly administered or targeted to the required site in vivo using appropriate viral vectors.

[0204] Alternatively, endogenous oct-3 gene expression can be reduced by targeting deoxyribonucleotide sequences complementary to the regulatory region of the oct-3 gene (i.e., the oct-3 promoter and/or enhancers) to form triple helical structures that prevent transcription of the oct-3 gene in target cells in the body (Helene, Anticancer Drug Res. 6:569, 1981; Helene et al., Ann. N.Y. Acad. Sci. 660:27, 1992; and Maher, Bioassays 14:807, 1992).

[0205] In addition, as discussed above, anti-sense moleceules, ribozymes, and peptide nucleic acids can be used to reduce oct-3 expression.

[0206] Assays for the Identification of Compounds that Ameliorate Disorders Associated with Aberrant OCT-3 Expression or Activity

[0207] Compounds, including, but not limited to, compounds identified via assay techniques such as those described above may be useful for the treatment of disorders associated with aberrant OCT-3 activity.

[0208] While animal model-based assays are particularly useful for the identification of such therapeutic compounds, cell-based assay systems are also very useful, particularly in combination with animal-model based assays. Such cell-based systems can include, for example, recombinant or non-recombinant cells which express oct-3. The effect of a selected modulatory compound on oct-3 expression can be measured using any of the above-described techniques for measuring OCT-3 protein or oct-3 mRNA, and the effect of a selected modulatory compound on OCT-3 activity can be measured by measuring the flux of a molecule transported by OCT-3.

[0209] Detection Assays

[0210] Portions or fragments of the cDNA sequences identified herein (and the corresponding complete gene sequences) can be used in numerous ways as polynucleotide reagents. For example, these sequences can be used to: (i) map their respective genes on a chromosome; and, thus, locate gene regions associated with genetic disease; (ii) identify an individual from a minute biological sample (tissue typing); and (iii) aid in forensic identification of a biological sample. These applications are described in the subsections below.

[0211] Chromosome Mapping

[0212] Once the sequence (or a portion of the sequence) of a gene has been isolated, this sequence can be used to map the location of the gene on a chromosome. This process is called chromosome mapping. Accordingly, portions or fragments of the oct-3 nucleotide sequences, described herein, can be used to map the location of the oct-3 genes on a chromosome. The mapping of the oct-3 gene sequences to chromosomes is an important first step in correlating these sequences with genes associated with disease.

[0213] Briefly, oct-3 genes can be mapped to chromosomes by preparing PCR primers (preferably 15-25 bp in length) from the oct-3 nucleotide sequences. Computer analysis of the oct-3 sequences can be used to predict primers that do not span more than one exon in the genomic DNA, thus complicating the amplification process. These primers can then be used for PCR screening of somatic cell hybrids containing individual human chromosomes. Only those hybrids containing the human gene corresponding to the oct-3 sequences will yield an amplified fragment.

[0214] Somatic cell hybrids are prepared by fusing somatic cells from different mammals (e.g., human and mouse cells). As hybrids of human and mouse cells grow and divide, they gradually lose human chromosomes in random order, but retain the mouse chromosomes. By using media in which mouse cells cannot grow, because they lack a particular enzyme, but human cells can, the one human chromosome that contains the gene encoding the needed enzyme, will be retained. By using various media, panels of hybrid cell lines can be established. Each cell line in a panel contains either a single human chromosome or a small number of human chromosomes, and a full set of mouse chromosomes, allowing easy mapping of individual genes to specific human chromosomes (D'Eustachio P. et al. (1983) Science 220:919-924). Somatic cell hybrids containing only fragments of human chromosomes can also be produced by using human chromosomes with translocations and deletions.

[0215] PCR mapping of somatic cell hybrids is a rapid procedure for assigning a particular sequence to a particular chromosome. Three or more sequences can be assigned per day using a single thermal cycler. Using the oct-3 nucleotide sequences to design oligonucleotide primers, sublocalization can be achieved with panels of fragments from specific chromosomes. Other mapping strategies which can similarly be used to map an oct-3 sequence to its chromosome include in situ hybridization (described in Fan, Y. et al. (1990) Proc. Natl. Acad. Sci. USA, 87:6223-27), pre-screening with labeled flow-sorted chromosomes, and pre-selection by hybridization to chromosome specific cDNA libraries.

[0216] Fluorescence in situ hybridization (FISH) of a DNA sequence to a metaphase chromosomal spread can further be used to provide a precise chromosomal location in one step. Chromosome spreads can be made using cells whose division has been blocked in metaphase by a chemical such as colcemid that disrupts the mitotic spindle. The chromosomes can be treated briefly with trypsin, and then stained with Giemsa. A pattern of light and dark bands develops on each chromosome, so that the chromosomes can be identified individually. The FISH technique can be used with a DNA sequence as short as 500 or 600 bases. However, clones larger than 1,000 bases have a higher likelihood of binding to a unique chromosomal location with sufficient signal intensity for simple detection. Preferably 1,000 bases, and more preferably 2,000 bases will suffice to get good results at a reasonable amount of time. For a review of this technique, see Verma et al., Human Chromosomes: A Manual of Basic Techniques (Pergamon Press, New York 1988).

[0217] Reagents for chromosome mapping can be used individually to mark a single chromosome or a single site on that chromosome, or panels of reagents can be used for marking multiple sites and/or multiple chromosomes. Reagents corresponding to noncoding regions of the genes actually are preferred for mapping purposes. Coding sequences are more likely to be conserved within gene families, thus increasing the chance of cross hybridizations during chromosomal mapping.

[0218] Once a sequence has been mapped to a precise chromosomal location, the physical position of the sequence on the chromosome can be correlated with genetic map data. (Such data are found, for example, in V. McKusick, Mendelian Inheritance in Man, available on-line through Johns Hopkins University Welch Medical Library, e.g., http://www.ncbi.nlm.nih.gov/Omim/). The relationship between a gene and a disease, mapped to the same chromosomal region, can then be identified through linkage analysis (co-inheritance of physically adjacent genes), described in, for example, Egeland, J. et al. (1987) Nature, 325:783-787.

[0219] Moreover, differences in the DNA sequences between individuals affected and unaffected with a disease associated with an oct-3 gene, can be determined. If a mutation is observed in some or all of the affected individuals but not in any unaffected individuals, then the mutation is likely to be the causative agent of the particular disease. Comparison of affected and unaffected individuals generally involves first looking for structural alterations in the chromosomes, such as deletions or translocations that are visible from chromosome spreads or detectable using PCR based on that DNA sequence. Ultimately, complete sequencing of genes from several individuals can be performed to confirm the presence of a mutation and to distinguish mutations from polymorphisms.

[0220] Tissue Typing

[0221] The OCT-3 sequences of the present invention can also be used to identify individuals from minute biological samples. The United States military, for example, is considering the use of restriction fragment length polymorphism (RFLP) for identification of its personnel. In this technique, an individual's genomic DNA is digested with one or more restriction enzymes, and probed on a Southern blot to yield unique bands for identification. This method does not suffer from the current limitations of “Dog Tags” which can be lost, switched, or stolen, making positive identification difficult. The sequences of the present invention are useful as additional DNA markers for RFLP (described in U.S. Pat. No. 5,272,057).

[0222] Furthermore, the sequences of the present invention can be used to provide an alternative technique which determines the actual base-by-base DNA sequence of selected portions of an individual's genome. Thus, the OCT-3 nucleotide sequences described herein can be used to prepare two PCR primers from the 5′ and 3′ ends of the sequences. These primers can then be used to amplify an individual's DNA and subsequently sequence it.

[0223] Panels of corresponding DNA sequences from individuals, prepared in this manner, can provide unique individual identifications, as each individual will have a unique set of such DNA sequences due to allelic differences. The sequences of the present invention can be used to obtain such identification sequences from individuals and from tissue. The oct-3 nucleotide sequences of the invention uniquely represent portions of the human genome. Allelic variation occurs to some degree in the coding regions of these sequences, and to a greater degree in the noncoding regions. It is estimated that allelic variation between individual humans occurs with a frequency of about once per each 500 bases. Each of the sequences described herein can, to some degree, be used as a standard against which DNA from an individual can be compared for identification purposes. Because greater numbers of polymorphisms occur in the noncoding regions, fewer sequences are necessary to differentiate individuals. The noncoding sequences of SEQ ID NOs: 1 and 3 can comfortably provide positive individual identification with a panel of perhaps 10 to 1,000 primers which each yield a noncoding amplified sequence of 100 bases. If predicted coding sequences, such as the coding sequence in SEQ ID NOs: 1 or 3 are used, a more appropriate number of primers for positive individual identification would be 500-2,000.

[0224] If a panel of reagents from oct-3 nucleotide sequences described herein is used to generate a unique identification database for an individual, those same reagents can later be used to identify tissue from that individual. Using the unique identification database, positive identification of the individual, living or dead, can be made from extremely small tissue samples.

[0225] Use of oct-3 Sequences in Forensic Biology

[0226] DNA-based identification techniques can also be used in forensic biology. Forensic biology is a scientific field employing genetic typing of biological evidence found at a crime scene as a means for positively identifying, for example, a perpetrator of a crime. To make such an identification, PCR technology can be used to amplify DNA sequences taken from very small biological samples such as tissues, e.g., hair or skin, or body fluids, e.g., blood, saliva, or semen found at a crime scene. The amplified sequence can then be compared to a standard, thereby allowing identification of the origin of the biological sample.

[0227] The sequences of the present invention can be used to provide polynucleotide reagents, e.g., PCR primers, targeted to specific loci in the human genome, which can enhance the reliability of DNA-based forensic identifications by, for example, providing another “identification marker” (i.e. another DNA sequence that is unique to a particular individual). As mentioned above, actual base sequence information can be used for identification as an accurate alternative to patterns formed by restriction enzyme generated fragments. Sequences targeted to noncoding regions of SEQ ID NOs: 1 or 3 are particularly appropriate for this use as greater numbers of polymorphisms occur in the noncoding regions, making it easier to differentiate individuals using this technique. Examples of polynucleotide reagents include the oct-3 nucleotide sequences or portions thereof, e.g., fragments derived from the noncoding regions of SEQ ID NOs:1 or 3 having a length of at least 20 bases, preferably at least 30 bases.

[0228] The oct-3 nucleotide sequences described herein can further be used to provide polynucleotide reagents, e.g., labeled or labelable probes which can be used in, for example, an in situ hybridization technique, to identify a specific tissue, e.g., brain tissue. This can be very useful in cases where a forensic pathologist is presented with a tissue of unknown origin. Panels of such oct-3 probes can be used to identify tissue by species and/or by organ type.

[0229] In a similar fashion, these reagents, e.g., oct-3 primers or probes can be used to screen tissue culture for contamination (i.e. screen for the presence of a mixture of different types of cells in a culture).

[0230] Therapeutic Dose

[0231] Toxicity and therapeutic efficacy of the polypeptides of the invention and the compounds that modulate their expression or activity can be determined by standard pharmaceutical procedures, using either cells in culture or experimental animals to determine the LD50 (the dose lethal to 50% of the population) and the ED50 (the dose therapeutically effective in 50% of the population). The dose ratio between toxic and therapeutic effects is the therapeutic index and it can be expressed as the ratio LD50/ED50. Polypeptides or other compounds that exhibit large therapeutic indices are preferred. While compounds that exhibit toxic side effects may be used, care should be taken to design a delivery system that targets such compounds to the site of affected tissue in order to minimize potential damage to uninfected cells and, thereby, reduce side effects.

[0232] The data obtained from the cell culture assays and animal studies can be used in formulating a range of dosage for use in humans. The dosage of such compounds lies preferably within a range of circulating concentrations that include the ED50 with little or no toxicity. The dosage may vary within this range depending upon the dosage form employed and the route of administration utilized. For any compound used in the method of the invention, the therapeutically effective dose can be estimated initially from cell culture assays. A dose can be formulated in animal models to achieve a circulating plasma concentration range that includes the IC50 (that is, the concentration of the test compound which achieves a half-maximal inhibition of symptoms) as determined in cell culture. Such information can be used to more accurately determine useful doses in humans. Levels in plasma may be measured, for example, by high performance liquid chromatography.

[0233] Formulations and Use

[0234] Pharmaceutical compositions for use in accordance with the present invention can be formulated in a conventional manner using one or more physiologically acceptable carriers or excipients. Thus, the compounds and their physiologically acceptable salts and solvates may be formulated for administration by inhalation or insufflation (either through the mouth or the nose) or oral, buccal, parenteral or rectal administration.

[0235] For oral administration, the pharmaceutical compositions may take the form of, for example, tablets or capsules prepared by conventional means with pharmaceutically acceptable excipients such as binding agents (e.g., pregelatinised maize starch, polyvinylpyrrolidone, or hydroxypropyl methylcellulose); fillers (e.g., lactose, microcrystalline cellulose, or calcium hydrogen phosphate); lubricants (e.g., magnesium stearate, talc, or silica); disintegrants (e.g., potato starch or sodium starch glycolate); or wetting agents (e.g., sodium lauryl sulphate). The tablets may be coated by methods well known in the art. Liquid preparations for oral administration may take the form of, for example, solutions, syrups or suspensions, or they may be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may be prepared by conventional means with pharmaceutically acceptable additives such as suspending agents (e.g., sorbitol syrup, cellulose derivatives, or hydrogenated edible fats); emulsifying agents (e.g., lecithin or acacia); non-aqueous vehicles (e.g., almond oil, oily esters, ethyl alcohol, or fractionated vegetable oils); and preservatives (e.g., methyl or propyl-p-hydroxybenzoates or sorbic acid). The preparations may also contain buffer salts, flavoring, coloring and sweetening agents as appropriate. Preparations for oral administration may be suitably formulated to give controlled release of the active compound.

[0236] For buccal administration the compositions may take the form of tablets or lozenges formulated in conventional manner.

[0237] For administration by inhalation, the compounds for use according to the present invention are conveniently delivered in the form of an aerosol spray presentation from pressurized packs or a nebulizer, with the use of a suitable propellant, for example, dichlorodifluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide or other suitable gas. In the case of a pressurized aerosol the dosage unit may be determined by providing a valve to deliver a metered amount. Capsules and cartridges of, for example, gelatin for use in an inhaler or insufflator may be formulated containing a powder mix of the compound and a suitable powder base such as lactose or starch.

[0238] The compounds may be formulated for parenteral administration by injection, for example, by bolus injection or continuous infusion. Formulations for injection may be presented in unit dosage form, for example, in ampoules or in multi-dose containers, with an added preservative. The compositions may take such forms as suspensions, solutions, or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilizing and/or dispersing agents. Alternatively, the active ingredient can be in powder form for constitution with a suitable vehicle, for example, sterile pyrogen-free water, before use.

[0239] The compounds can also be formulated in rectal compositions such as suppositories or retention enemas, for example, containing conventional suppository bases such as cocoa butter or other glycerides.

[0240] In addition to the formulations described previously, the compounds may also be formulated as a depot preparation. Such long acting formulations may be administered by implantation (e.g., subcutaneously or intramuscularly) or by intramuscular injection. Thus, for example, the compounds may be formulated with suitable polymeric or hydrophobic materials (e.g., as an emulsion in an acceptable oil) or ion exchange resins, or as sparingly soluble derivatives, for example, as a sparingly soluble salt.

[0241] The compositions can, if desired, be presented in a pack or dispenser device which may contain one or more unit dosage forms containing the active ingredient. The pack can, for example, comprise metal or plastic foil, such as a blister pack. The pack or dispenser device can be accompanied by instructions for administration.

[0242] The therapeutic compositions of the invention can also contain a carrier or excipient, many of which are known to persons of ordinary skill in the art. Excipients that can be used include buffers (e.g., citrate buffer, phosphate buffer, acetate buffer, and bicarbonate buffer), amino acids, urea, alcohols, ascorbic acid, phospholipids, proteins (e.g., serum albumin), EDTA, sodium chloride, liposomes, mannitol, sorbitol, and glycerol.

[0243] The nucleic acids, polypeptides, antibodies, or other modulatory compounds of the invention (i.e., compounds that alter the expression of oct-3 or the activity of OCT-3) can be administered by any standard route of administration. For example, administration can be parenteral, intravenous, subcutaneous, intramuscular, intracranial, intraorbital, opthalmic, intraventricular, intracapsular, intraspinal, intracisternal, intraperitoneal, transmucosal, or oral. The modulatory compound can be formulated in various ways, according to the corresponding route of administration. For example, liquid solutions can be made for ingestion or injection; gels or powders can be made for ingestion, inhalation, or topical application. Methods for making such formulations are well known and can be found in, for example, “Remington's Pharmaceutical Sciences.” It is expected that the preferred route of administration will be intravenous.

[0244] Compounds Transported by OCT-3

[0245] Compounds that are transported across cellular membranes by an OCT-3 polypeptide of the invention can be identified by transiently expressing an oct-3 gene of the invention in cells (e.g., a host cell such as 293) and measuring the transport of candidate molecules across the plasma membranes of those cells. The expression of an OCT-3 polypeptide could be confirmed by, for example, performing immunohistochemistry to detect either OCT-3 or an epitope tag placed on the OCT-3 polypeptide. To measure the transport of candidate molecules across the plasma membrane, one could directly measure the uptake of radiolabelled molecules such as TEA, dopamine, serotonin, histamine, and acetylcholine. This assay could be performed, for example, by incubating the cells expressing the OCT-3 transporter with radiolabelled candidate molecules for 1 hour at room temperature, washing the cells with an ice cold buffer, lysing the cells, and measuring the radioactivity in scintillant in a beta counter. Persons of ordinary skill in the art may consult Martel et al. (Arch. Pharmacol. 354:320-326, 1996), if necessary, for a more detailed protocol.

[0246] The assay described above can be used to determine whether any given polypeptide functions as an OCT-3 polypeptide of the invention. To make this determination, one would simply perform the assay using the OCT-3 polypeptide described herein and a second, putative OCT-3 polypeptide (such as a polypeptide that differs from SEQ ID NOs:2, 4 or 6 by the addition, deletion, or substitution of one or more amino acid residues), in parallel. The putative OCT-3 polypeptide would prove to be within the scope of the present invention if it exhibited 20%, 40%, or 50% of the activity of the full-length, mature form of OCT-3. Preferably, a candidate OCT-3 molecule would exhibit 75%, 80%, or even 90% (or more, e.g., 95% or even 99%) of the activity of OCT-3, as disclosed herein. Candidate OCT-3 polypeptides that are substantially identical to SEQ ID NOs:2, 4, or 6 may even exhibit greater biological activity (i.e., serve as more effective transporters) than the wild-type polypeptide itself.

EXAMPLES

Example 1

Cloning of Rat oct-3

[0247] A cDNA library in plasmid pMET7 was prepared using oligo dT-purified RNA isolated from adult rat frontal cortex tissue. The library was plated, colonies were selected randomly, and the 5′ ends of the cDNA inserts were sequenced (5′ sample sequencing). Each sequence (5′ expressed sequence tag (EST)) was compared with sequences in public databases using the BLAST algorithm. One such 5′ EST had an extremely low degree of similarity with OCT-2 sequences identified in pig and rat, and lesser similarity to nucleic acid molecules encoding other organic cation transport proteins. The sequence comparison indicated that the clone identified from the rat library was a partial length clone having a coding sequence that extended from approximately the 5′ end of the sixth putative transmembrane domain through the 3′ end of the gene. This clone was sequenced by sequentially “walking” from both the 5′ and the 3′ ends of the molecule. A hydropathy plot of the coding region indicated 7 transmembrane domains corresponding, approximately, in position to the sixth through the twelfth transmembrane domains of OCT-2. No stop codons were found in the homologous reading frame and a poly-A tail was detected. These features indicate that this is a legitimate, functional mRNA, rather than a pseudogene.

[0248] The 5′ EST sequence was used to prepare a DNA probe that was labelled and hybridized to Northern blots. Hybridization to a blot containing several rat tissues (a rat multiple tissue Northern blot was purchased from Clontech) indicated a robust signal corresponding to a 2.3 kb transcript predominantly in brain tissues. Extended exposure of the autoradiogram prepared from the Northern blot indicated the presence of similar bands in a subset of other tissues including kidney, heart, lung, testis, spleen, and liver.

[0249] The rat RNA probe was also hybridized to a Northern blot containing samples from different regions of the human CNS, including spinal cord and cortex. A single band was observed in all samples. The intensity of labelling was similar in all samples, although somewhat reduced in the spinal cord.

[0250] The rat oct-3 clone was used to make probes for in situ hybridization experiments. Experiments with various coronal sections of rat brain showed strong hybridization at the cell bodies of neurons. No significant hybridization was observed to non-neuronal cells. The hybridization signal at some neurons, for example, Purkinje cells, was relatively weak, while in other cells, for example, granule cells of the hippocampus and cerebellum, the hybridization signal was intense.

[0251] The sequence of the rat cDNA clone described in this example and the predicted amino acid sequence are shown in FIGS. 3A-3B and SEQ ID NOs:5 and 6.

EXAMPLE 2

Cloning of Human oct-3

[0252] The rat octclone described in Example 1 was used to identify a portion of a human oct-3 cDNA clone, which was used to screen a human cerebellum cDNA library. Seventy-seven clones were identified, and the 5′ ends of 10 of these were sequenced and found to represent the same gene. Restriction digests of the plasmids showed two classes of insert lengths. One insert was approximately 1.5 kb and the other was approximately 2.4 kb. Two clones, designated “g” and “a,” were selected as examples of each class and fully sequenced. Clone “a” has 12 hydrophobic transmembrane regions (as predicted by the Kyte and Doolittle algorithm), which is characteristic of transporter proteins. The sequence of clone “a” is shown in FIGS. 1A-1C (SEQ ID NO: 1). Clone “g” represents a truncated mRNA whose coding region includes the first six TM domains. The sequence of clone “g” is shown in FIGS. 2A-2B (SEQ ID NO:3).

Example 3

Expression of oct-3 mRNA in Rat Models of Pain

[0253] To study the expression of oct-3 in animal models of pain, rats were subjected to the following procedures: ligation of the sciatic nerve to produce chronic constriction injury (Bennett G J & Xie Y K, 1988; Pain 33; 87-107), plantar injection of complete Freund's adjuvant (Stein C, Millan M J and Herz A, 1988; Pharmacol Biochem Behav-31; 445-451) to produce inflammatory pain, or axotomy of the sciatic nerve (Curtis et al., 1994; Neuron 12; 191-204) to produce chronic pain. Total RNA from spinal cord and dorsal root ganglia was prepared by a single step extraction method using RNA STAT-60 according to the manufacturer's instructions (TelTest, Inc). Each RNA preparation was treated with DNase I (Ambion) at 37° C. for 1 hour. DNAse I treatment was determined to be complete if the sample required at least 38 PCR amplification cycles to reach a threshold level of fluorescence using 18S as an internal amplicon reference. The integrity of the RNA samples following DNase I treatment was confirmed by 1.2% agarose gel electrophoresis. After phenol extraction cDNA was prepared from the sample using the TaqMan® reverse transcription reagent (PE Applied Biosystems). A negative control of RNA without reverse transcriptase was mock reverse transcribed for each RNA sample.

[0254] Expression of the rat ortholog of human oct-3 was measured by TaqMan® quantitative PCR (PE Applied Biosystems) in cDNA prepared from a variety of normal and diseased (e.g., pain models) tissues.

[0255] Probes were designed by PrimerExpress software (PE Biosystems) based on the sequence of the rat oct-3 gene. Each rat oct-3 gene probe was labeled using FAM (6-carboxyfluorescein), and the 18S reference probe was labeled with a different fluorescent dye, VIC. The differential labeling of the target gene and internal reference gene thus enabled measurement in the same well. Forward and reverse primers and the probes for both 18S and target gene were added to the TaqMan® Universal PCR Master Mix (PE Applied Biosystems). 200 nM of forward and reverse primers plus 100 nM probe for 18S and 900 nM forward and reverse primers plus 250 nM probe for the target gene were used for each TaqMan® run. TaqMan® matrix experiments were carried out on an ABI PRISM 7700 Sequence Detection System (PE Applied Biosystems). The thermal cycler conditions were as follows: hold for 2 min at 50° C. and 10 min at 95° C., followed by two-step PCR for 40 cycles of 95° C. for 15 sec followed by 60° C. for 1 min.

[0256] The following method was used to quantitatively calculate rat oct-3 gene expression in the various tissues relative to 18S expression in the same tissue. The threshold cycle (Ct) value is defined as the cycle at which a statistically significant increase in fluorescence is detected. A lower Ct value is indicative of a higher mRNA expression. The Ct value of the rat oct-3 gene is normalized by subtracting the Ct value of the 18S to obtain a &Dgr;Ct value using the following formula: &Dgr;Ct=averageCtrat oct-3−averageCt18S Expression is then calibrated against NTC (no template control). The &Dgr;Ct value for the calibrator sample is then subtracted from &Dgr;Ct for each tissue sample according to the following formula: &Dgr;&Dgr;Ct=&Dgr;Ct−Sample−&Dgr;Ct−calibrator. Relative expression is then calculated using the arithmetic formula given by 2−&Dgr;&Dgr;Ct. Expression of the target rat oct-3 gene in each of the tissues tested is then graphically represented as discussed in more detail below.

[0257] The results indicated significant rat oct-3 expression in brain, spinal cord, dorsal root ganglion and superior cervical ganglion.

[0258] Deposit Statement

[0259] The subject clones have been deposited under conditions that assure that access to them will be available during the pendency of the patent application in which they are disclosed to those determined by the Commissioner of Patents and Trademarks to be entitled thereto under 37 C.F.R. §1.14 and 35 U.S.C. §122. More specifically, the clones described herein as “g” and “a” were deposited with the American Type Culture Collection and assigned accession numbers 98518 and 98519, respectively.

Claims

1. A method for identifying a compound capable of treating a pain disorder comprising assaying the ability of the compound to modulate the expression of an organic cation transporter 3 (OCT-3) nucleic acid, thereby identifying a compound capable of treating a pain disorder.

2. The method of claim 1, wherein the oct-3 nucleic acid is selected from the group consisting of:

a) a nucleic acid molecule comprising the nucleotide sequence set forth in SEQ ID NO:1, 3, or 5; and

b) a nucleic acid molecule comprising a nucleotide sequence which is at least 80 percent identical to the nucleotide sequence of SEQ ID NO: 1, 3, or 5.

3. A method for identifying a compound capable of treating a pain disorder comprising assaying the ability of the compound to modulate the activity of an organic cation transporter 3 (OCT-3) polypeptide, thereby identifying a compound capable of treating a pain disorder.

4. The method of claim 3, wherein the OCT-3 polypeptide is selected from the group consisting of:

a) a polypeptide comprising the amino acid sequence set forth in SEQ ID NO:2,4, or 6; and

b) a polypeptide comprising a polypeptide sequence which is at least 70 percent identical to the polypeptide sequence of SEQ ID NO:2, 4, or 6.

5. A method for identifying a compound capable of modulating an organic cation transporter 3 (OCT-3) activity, comprising:

(a) contacting a cell which expresses OCT-3 with a test compound; and

(b) assaying the ability of the test compound to modulate the expression of an OCT-3 nucleic acid or the activity of an OCT-3 polypeptide, thereby identifying a compound capable of modulating an OCT-3 activity.

6. A method for identifying a compound capable of modulating an organic cation transporter 3 (OCT-3) activity, comprising:

(a) contacting a polypeptide comprising the amino acid sequence of SEQ ID NO:2, 4, or 6 with a test compound; and

(b) assaying the ability of the test compound to modulate an activity of the polypeptide, thereby identifying a compound capable of modulating an OCT-3 activity.

7. A method for modulating an OCT-3 activity comprising contacting an OCT-3 polypeptide or a cell expressing an OCT-3 polypeptide with a compound which binds to the polypeptide in a sufficient concentration to modulate the OCT-3 activity.

8. The method of claim 7, wherein the OCT-3 polypeptide comprises an amino acid sequence which is at least 80 percent identical to the amino acid sequence of SEQ ID NO:2, 4, or 6, wherein said percent identity is calculated using the ALIGN program for comparing amino acid sequences, a PAM120 weight residue table, a gap length penalty of 12, and a gap penalty of 4.

9. The method of any of claims 1, 3, 5, 6 and 7, wherein the compound or modulator is a small molecule.

10. The method of any of claims 1, 3, 5, 6 and 7, wherein the compound or modulator is an anti OCT-3 antibody.

11. The method of any of claims 1, 3, 5, 6 and 7, wherein the compound or modulator is an OCT-3 ribozyme.

12. A method for treating a subject having a pain disorder characterized by aberrant OCT-3 polypeptide activity or aberrant OCT-3 nucleic acid expression, comprising administering to the subject an OCT-3 modulator, thereby treating the subject having a pain disorder.

13. The method of claim 9, wherein the modulator is selected from the group consisting of a small molecule OCT-3 agonist, a small molecule OCT-3 antagonist, an anti-OCT-3 antibody, an antisense oct-3 molecule, and an oct-3 ribozyme.

14. A pharmaceutical formulation for the treatment of a pain disorder, comprising a compound that activates an organic cation transporter 3 (OCT-3) polypeptide activity or an OCT-3 nucleic acid expression, mixed with a pharmaceutically acceptable carrier.

15. The pharmaceutical formulation of claim 14, wherein the compound is selected from the group consisting of a small molecule OCT-3 agonist, a small molecule OCT-3 antagonist, an anti-OCT-3 antibody, an antisense oct-3 molecule, and an oct-3 ribozyme.

16. A genetically engineered nonhuman mammal in which the expression of an oct-3 gene has been inactivated.

17. A transgenic animal which expresses a human oct-3 gene.